目录
1.整型
1.1参数signed和unsigned
1.2参数zerofill
1.3参数auto_increment
2.数字类型
2.1floor()向下取整
2.2随机函数rand()
2.3重复函数repeat()
3.字符串类型
3.1length()查看字节长度，char_length()查看字符长度
3.2字符集
3.2.1查看默认字符集
3.2.2查看已经创建的数据库的字符集
3.2.3修改已经创建的数据库的字符集
3.2.4修改mysql默认字符集
3.2.5两条转换表字符集的语句
3.2.6查看支持的字符集
3.3hex()函数
3.4cast()函数
3.5排序规则collation
3.6对于密码的加密，md5()函数
3.7upper()和lower()函数
3.8concat()和concat_ws()函数
3.9lpad()和rpad()函数
4.enum&set类型
5.时间类型
5.1日期函数
编辑 5.1.1now()函数
5.1.2now()和sysdate()的区别
5.1.3date_add()和date_sub()函数
5.1.4date_format()函数
6.json类型
6.1json类型相关函数
6.1.1json_extract()函数
6.1.2json_remove()函数
mysql的数据类型有：整型、数字类型、字符串类型、日期类型、json类型等主要类型
1.整型
1.1参数signed和unsigned
可以创建有符号(signed)和无符号(unsigned)的整型类型
(root@localhost) [(none)]> use python;
Database changed
(root@localhost) [python]> create table z (a int unsigned,b tinyint signed);
Query OK, 0 rows affected (0.58 sec)
(root@localhost) [python]> insert into z values(1,1);
Query OK, 1 row affected (0.13 sec)
(root@localhost) [python]> insert into z values(-1,1);
ERROR 1264 (22003): Out of range value for column 'a' at row 1
(root@localhost) [python]> insert into z values(1,-1);
Query OK, 1 row affected (0.05 sec)
(root@localhost) [python]> select * from z;
+------+------+
| a | b |
+------+------+
| 1 | 1 |
| 1 | -1 |
+------+------+
2 rows in set (0.00 sec)1.2参数zerofill
查看创建表ddl有int(10)和tinyint(4)，其中10和4代表显示的数值总长度，长度不够用0填充
(root@localhost) [python]> show create table z\G
*************************** 1. row ***************************
Table: z
Create Table: CREATE TABLE `z` (
`a` int(10) unsigned DEFAULT NULL,
`b` tinyint(4) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1
1 row in set (0.04 sec)
(root@localhost) [python]> alter table z change column a a int unsigned zerofill;
Query OK, 0 rows affected (0.06 sec)
Records: 0 Duplicates: 0 Warnings: 0
(root@localhost) [python]> select * from z;
+------------+------+
| a | b |
+------------+------+
| 0000000001 | 1 |
| 0000000001 | -1 |
+------------+------+
2 rows in set (0.00 sec)
(root@localhost) [python]> show create table z\G
*************************** 1. row ***************************
Table: z
Create Table: CREATE TABLE `z` (
`a` int(10) unsigned zerofill DEFAULT NULL,
`b` tinyint(4) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1
1 row in set (0.00 sec)
可以修改显示的总长度
(root@localhost) [python]> alter table z change column a a int(4) unsigned zerofill;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
(root@localhost) [python]> select * from z;
+------+------+
| a | b |
+------+------+
| 0001 | 1 |
| 0001 | -1 |
+------+------+
2 rows in set (0.00 sec)
(root@localhost) [python]> show create table z\G
*************************** 1. row ***************************
Table: z
Create Table: CREATE TABLE `z` (
`a` int(4) unsigned zerofill DEFAULT NULL,
`b` tinyint(4) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1
1 row in set (0.00 sec)可以正常插入比显示长度更大的值
(root@localhost) [python]> insert into z values(20000,2);
Query OK, 1 row affected (0.00 sec)
(root@localhost) [python]> select * from z;
+-------+------+
| a | b |
+-------+------+
| 0001 | 1 |
| 0001 | -1 |
| 20000 | 2 |
+-------+------+
3 rows in set (0.00 sec)1.3参数auto_increment
设置该参数，主键自动递增，select last_insert_id()查询上一次自增id值是多少，表数据量大主键自增字段建议用bigint类型
(root@localhost) [python]> truncate table z;
Query OK, 0 rows affected (0.13 sec)
(root@localhost) [python]> alter table z change column a a int auto_increment primary key;
Query OK, 0 rows affected (0.11 sec)
Records: 0 Duplicates: 0 Warnings: 0
(root@localhost) [python]> show create table z\G
*************************** 1. row ***************************
Table: z
Create Table: CREATE TABLE `z` (
`a` int(11) NOT NULL AUTO_INCREMENT,
`b` tinyint(4) DEFAULT NULL,
PRIMARY KEY (`a`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
1 row in set (0.00 sec)
(root@localhost) [python]> insert into z values(null,10);
Query OK, 1 row affected (0.01 sec)
(root@localhost) [python]> insert into z values(null,20);
Query OK, 1 row affected (0.01 sec)
(root@localhost) [python]> insert into z(b) values(30);
Query OK, 1 row affected (0.05 sec)
(root@localhost) [python]> insert into z values(40);
ERROR 1136 (21S01): Column count doesn't match value count at row 1
(root@localhost) [python]> select * from z;
+---+------+
| a | b |
+---+------+
| 1 | 10 |
| 2 | 20 |
| 3 | 30 |
+---+------+
3 rows in set (0.00 sec)
(root@localhost) [python]> select last_insert_id();
+------------------+
| last_insert_id() |
+------------------+
| 3 |
+------------------+
1 row in set (0.06 sec)自增字段值在不重启数据库的情况下不会回溯，只会越来越大
(root@localhost) [python]> delete from z where b=30;
Query OK, 1 row affected (0.06 sec)
(root@localhost) [python]> insert into z values(null,30);
Query OK, 1 row affected (0.04 sec)
(root@localhost) [python]> select * from z;
+---+------+
| a | b |
+---+------+
| 1 | 10 |
| 2 | 20 |
| 4 | 30 |
+---+------+
3 rows in set (0.00 sec)自增字段在删除select last_insert_id()的值后，重启数据库会回溯，查看ddl，AUTO_INCREMENT=7
(root@localhost) [python]> select * from z;
+---+------+
| a | b |
+---+------+
| 1 | 10 |
| 2 | 20 |
| 5 | 40 |
| 6 | 30 |
+---+------+
4 rows in set (0.00 sec)
(root@localhost) [python]> show create table z\G
*************************** 1. row ***************************
Table: z
Create Table: CREATE TABLE `z` (
`a` int(11) NOT NULL AUTO_INCREMENT,
`b` tinyint(4) DEFAULT NULL,
PRIMARY KEY (`a`)
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=latin1
1 row in set (0.00 sec)
(root@localhost) [python]> delete from z where a=6;
Query OK, 1 row affected (0.01 sec)
(root@localhost) [python]> delete from z where a=5;
Query OK, 1 row affected (0.01 sec)
(root@localhost) [python]> select * from z;
+---+------+
| a | b |
+---+------+
| 1 | 10 |
| 2 | 20 |
+---+------+
2 rows in set (0.00 sec)
删除a=6、a=5后重启数据库查看ddl，AUTO_INCREMENT=3，此时就回溯了，再次插入数据a=3、a=4就回来了，线上删除的值就又出现了，会乱掉，这个问题在mysql8.0得到解决
(root@localhost) [python]> show create table z\G
*************************** 1. row ***************************
Table: z
Create Table: CREATE TABLE `z` (
`a` int(11) NOT NULL AUTO_INCREMENT,
`b` tinyint(4) DEFAULT NULL,
PRIMARY KEY (`a`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=latin1
1 row in set (0.00 sec)
(root@localhost) [python]> select * from z;
+---+------+
| a | b |
+---+------+
| 1 | 10 |
| 2 | 20 |
+---+------+
2 rows in set (0.00 sec)
(root@localhost) [python]> insert into z values(null,30);
Query OK, 1 row affected (0.00 sec)
(root@localhost) [python]> insert into z values(null,40);
Query OK, 1 row affected (0.01 sec)
(root@localhost) [python]> select * from z;
+---+------+
| a | b |
+---+------+
| 1 | 10 |
| 2 | 20 |
| 3 | 30 |
| 4 | 40 |
+---+------+
4 rows in set (0.00 sec)
(root@localhost) [python]>mysql8.0解决自增字段回溯问题，AUTO_INCREMENT值持久化
[root@localhost ~]# mysql -S/tmp/mysql.sock80 -uroot -p123456
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 19
Server version: 8.0.35 MySQL Community Server - GPL
Copyright (c) 2000, 2023, Oracle and/or its affiliates.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
(root@localhost) [(none)]> create database zs;
Query OK, 1 row affected (0.42 sec)
(root@localhost) [(none)]> use zs
Database changed
(root@localhost) [zs]> create table z (a bigint auto_increment primary key,b tinyint);
Query OK, 0 rows affected (1.36 sec)
(root@localhost) [zs]> show create table z\G;
*************************** 1. row ***************************
Table: z
Create Table: CREATE TABLE `z` (
`a` bigint NOT NULL AUTO_INCREMENT,
`b` tinyint DEFAULT NULL,
PRIMARY KEY (`a`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci
1 row in set (0.22 sec)
ERROR:
No query specified
(root@localhost) [zs]> insert into z values(null,10);
Query OK, 1 row affected (0.08 sec)
(root@localhost) [zs]> insert into z values(null,20);
Query OK, 1 row affected (0.05 sec)
(root@localhost) [zs]> insert into z values(null,30);
Query OK, 1 row affected (0.05 sec)
(root@localhost) [zs]> insert into z values(null,40);
Query OK, 1 row affected (0.01 sec)
(root@localhost) [zs]> show create table z\G;
*************************** 1. row ***************************
Table: z
Create Table: CREATE TABLE `z` (
`a` bigint NOT NULL AUTO_INCREMENT,
`b` tinyint DEFAULT NULL,
PRIMARY KEY (`a`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci
1 row in set (0.00 sec)
ERROR:
No query specified
(root@localhost) [zs]> select * from z;
+---+------+
| a | b |
+---+------+
| 1 | 10 |
| 2 | 20 |
| 3 | 30 |
| 4 | 40 |
+---+------+
4 rows in set (0.01 sec)
(root@localhost) [zs]> delete from z where a=4;
Query OK, 1 row affected (0.06 sec)
(root@localhost) [zs]> delete from z where a=3;
Query OK, 1 row affected (0.05 sec)
(root@localhost) [zs]> select * from z;
+---+------+
| a | b |
+---+------+
| 1 | 10 |
| 2 | 20 |
+---+------+
2 rows in set (0.00 sec)
(root@localhost) [zs]> show create table z\G;
*************************** 1. row ***************************
Table: z
Create Table: CREATE TABLE `z` (
`a` bigint NOT NULL AUTO_INCREMENT,
`b` tinyint DEFAULT NULL,
PRIMARY KEY (`a`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci
1 row in set (0.00 sec)
ERROR:
No query specified
(root@localhost) [zs]> exit
Bye
[root@localhost ~]# mysqld_multi stop 80
[root@localhost ~]# mysqld_multi report
Reporting MySQL servers
MySQL server from group: mysqld32 is not running
MySQL server from group: mysqld1 is not running
MySQL server from group: mysqld2 is not running
MySQL server from group: mysqld80 is not running
[root@localhost ~]# mysqld_multi start 80
[root@localhost ~]# mysqld_multi report
Reporting MySQL servers
MySQL server from group: mysqld32 is not running
MySQL server from group: mysqld1 is not running
MySQL server from group: mysqld2 is not running
MySQL server from group: mysqld80 is running
[root@localhost ~]# mysql -S/tmp/mysql.sock80 -uroot -p123456
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 9
Server version: 8.0.35 MySQL Community Server - GPL
Copyright (c) 2000, 2023, Oracle and/or its affiliates.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
(root@localhost) [(none)]> use zs;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
(root@localhost) [zs]> show create table z\G;
*************************** 1. row ***************************
Table: z
Create Table: CREATE TABLE `z` (
`a` bigint NOT NULL AUTO_INCREMENT,
`b` tinyint DEFAULT NULL,
PRIMARY KEY (`a`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci
1 row in set (0.00 sec)
ERROR:
No query specified
(root@localhost) [zs]> select * from z;
+---+------+
| a | b |
+---+------+
| 1 | 10 |
| 2 | 20 |
+---+------+
2 rows in set (0.00 sec)
(root@localhost) [zs]> insert into z values(null,30);
Query OK, 1 row affected (0.01 sec)
(root@localhost) [zs]> insert into z values(null,40);
Query OK, 1 row affected (0.00 sec)
(root@localhost) [zs]> select * from z;
+---+------+
| a | b |
+---+------+
| 1 | 10 |
| 2 | 20 |
| 5 | 30 |
| 6 | 40 |
+---+------+
4 rows in set (0.00 sec)
(root@localhost) [zs]>int类型总结
- 推荐不要使用UNSIGNED
- 范围本质上没有大的改变
- UNSIGNED可能会有溢出现象发生
- 自增INT类型主键建议使用BIGINT
2.数字类型
一般建议用decimal
2.1floor()向下取整
(root@localhost) [(none)]> select floor(1.5);
+------------+
| floor(1.5) |
+------------+
| 1 |
+------------+
1 row in set (0.00 sec)
(root@localhost) [(none)]> select floor(1.9);
+------------+
| floor(1.9) |
+------------+
| 1 |
+------------+
1 row in set (0.00 sec)
(root@localhost) [(none)]> select floor(-1.9);
+-------------+
| floor(-1.9) |
+-------------+
| -2 |
+-------------+
1 row in set (0.00 sec)2.2随机函数rand()
(root@localhost) [(none)]> select rand() ;
+-------------------+
| rand() |
+-------------------+
| 0.590530601880076 |
+-------------------+
1 row in set (0.00 sec)
(root@localhost) [(none)]> select rand() ;
+--------------------+
| rand() |
+--------------------+
| 0.1034116913596277 |
+--------------------+
1 row in set (0.00 sec)1~100随机整数
(root@localhost) [(none)]> select floor(1+rand()*99);
+--------------------+
| floor(1+rand()*99) |
+--------------------+
| 74 |
+--------------------+
1 row in set (0.00 sec)
(root@localhost) [(none)]> select floor(1+rand()*99);
+--------------------+
| floor(1+rand()*99) |
+--------------------+
| 42 |
+--------------------+
1 row in set (0.00 sec)
(root@localhost) [(none)]> select floor(1+rand()*99);
+--------------------+
| floor(1+rand()*99) |
+--------------------+
| 85 |
+--------------------+
1 row in set (0.00 sec)2.3重复函数repeat()
(root@localhost) [(none)]> select repeat(1,3);
+-------------+
| repeat(1,3) |
+-------------+
| 111 |
+-------------+
1 row in set (0.00 sec)
(root@localhost) [(none)]> select repeat(32,3);
+--------------+
| repeat(32,3) |
+--------------+
| 323232 |
+--------------+
1 row in set (0.00 sec)
(root@localhost) [(none)]> select repeat('b',5);
+---------------+
| repeat('b',5) |
+---------------+
| bbbbb |
+---------------+
1 row in set (0.00 sec)
(root@localhost) [(none)]> select repeat('ba',4);
+----------------+
| repeat('ba',4) |
+----------------+
| babababa |
+----------------+
1 row in set (0.00 sec)字符串或数字变长
(root@localhost) [mysql]> select repeat('a',floor(1+rand()*99));
+-----------------------------------------------------------------------------------------------------+
| repeat('a',floor(1+rand()*99)) |
+-----------------------------------------------------------------------------------------------------+
| aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa |
+-----------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
(root@localhost) [mysql]> select repeat('a',floor(1+rand()*99));
+--------------------------------------------+
| repeat('a',floor(1+rand()*99)) |
+--------------------------------------------+
| aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa |
+--------------------------------------------+
1 row in set (0.00 sec)
(root@localhost) [mysql]> select repeat('b1',floor(1+rand()*20));
+---------------------------------+
| repeat('b1',floor(1+rand()*20)) |
+---------------------------------+
| b1b1b1 |
+---------------------------------+
1 row in set (0.00 sec)
(root@localhost) [mysql]> select repeat('b1',floor(1+rand()*20));
+---------------------------------+
| repeat('b1',floor(1+rand()*20)) |
+---------------------------------+
| b1b1b1b1b1b1b1b1b1 |
+---------------------------------+
1 row in set (0.00 sec)3.字符串类型
char(n)和varchar(n)中的n代表字符，有字符集
(root@localhost) [python]> drop table z;
Query OK, 0 rows affected (0.72 sec)
(root@localhost) [python]> create table z (a char(1),b varchar(3),c binary(1),d varbinary(3));
Query OK, 0 rows affected (0.02 sec)
(root@localhost) [python]> insert into z values('a','bbb','c','ddd');
Query OK, 1 row affected (0.01 sec)
(root@localhost) [python]> select * from z;
+------+------+------+------+
| a | b | c | d |
+------+------+------+------+
| a | bbb | c | ddd |
+------+------+------+------+
1 row in set (0.00 sec)
(root@localhost) [python]> show create table z\G
*************************** 1. row ***************************
Table: z
Create Table: CREATE TABLE `z` (
`a` char(1) DEFAULT NULL,
`b` varchar(3) DEFAULT NULL,
`c` binary(1) DEFAULT NULL,
`d` varbinary(3) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1
1 row in set (0.00 sec)
(root@localhost) [python]> insert into z values('紫','bbc','x','ooo');
ERROR 1366 (HY000): Incorrect string value: '\xE7\xB4\xAB' for column 'a' at row 1
(root@localhost) [python]> alter table z convert to charset utf8mb4;
Query OK, 1 row affected (0.04 sec)
Records: 1 Duplicates: 0 Warnings: 0
(root@localhost) [python]> show create table z\G
*************************** 1. row ***************************
Table: z
Create Table: CREATE TABLE `z` (
`a` char(1) DEFAULT NULL,
`b` varchar(3) DEFAULT NULL,
`c` binary(1) DEFAULT NULL,
`d` varbinary(3) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
1 row in set (0.00 sec)
(root@localhost) [python]> insert into z values('紫','bbc','x','ooo');
Query OK, 1 row affected (0.00 sec)
(root@localhost) [python]> insert into z values('x','bbc','紫','ooo');
ERROR 1406 (22001): Data too long for column 'c' at row 13.1length()查看字节长度，char_length()查看字符长度
(root@localhost) [python]> select length('紫'),char_length('紫');
+---------------+--------------------+
| length('紫') | char_length('紫') |
+---------------+--------------------+
| 3 | 1 |
+---------------+--------------------+
1 row in set (0.00 sec)3.2字符集
mysql中的字符集最小是在列级别上
3.2.1查看默认字符集
(root@localhost) [python]> show variables like '%character%';
+--------------------------+----------------------------------------------------------------+
| Variable_name | Value |
+--------------------------+----------------------------------------------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | latin1 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | utf8mb4 |
| character_set_system | utf8 |
| character_sets_dir | /usr/local/mysql-5.7.44-linux-glibc2.12-x86_64/share/charsets/ |
+--------------------------+----------------------------------------------------------------+3.2.2查看已经创建的数据库的字符集
(root@localhost) [zs]> show create database python;
+----------+-------------------------------------------------------------------+
| Database | Create Database |
+----------+-------------------------------------------------------------------+
| python | CREATE DATABASE `python` /*!40100 DEFAULT CHARACTER SET latin1 */ |
+----------+-------------------------------------------------------------------+
1 row in set (0.00 sec)3.2.3修改已经创建的数据库的字符集
(root@localhost) [python]> alter database python charset utf8mb4;
Query OK, 1 row affected (0.00 sec)
(root@localhost) [python]> show create database python;
+----------+--------------------------------------------------------------------+
| Database | Create Database |
+----------+--------------------------------------------------------------------+
| python | CREATE DATABASE `python` /*!40100 DEFAULT CHARACTER SET utf8mb4 */ |
+----------+--------------------------------------------------------------------+
1 row in set (0.00 sec)3.2.4修改mysql默认字符集
在my.cnf中加入参数
[mysqld]
character_set_server=utf8mb4
3.2.5两条转换表字符集的语句
alter table t charset utf8mb4;与alter table t convert to charset(或者character set) utf8mb4;的不同，前者对已经存在的列不进行字符集转换，只对新增列转换，后者是对已经存在的列和新增列都转换，旧的字符集是新的字符集的子集，在生产上要注意转换字符集是要锁表的，要小心
(root@localhost) [python]> drop table t;
Query OK, 0 rows affected (0.01 sec)
(root@localhost) [python]> create table t(a varchar(10),b char(2)) charset gbk;
Query OK, 0 rows affected (0.04 sec)
(root@localhost) [python]> show create table t\G;
*************************** 1. row ***************************
Table: t
Create Table: CREATE TABLE `t` (
`a` varchar(10) DEFAULT NULL,
`b` char(2) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=gbk
1 row in set (0.00 sec)
ERROR:
No query specified
(root@localhost) [python]> alter table t charset utf8mb4;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
(root@localhost) [python]> show create table t\G;
*************************** 1. row ***************************
Table: t
Create Table: CREATE TABLE `t` (
`a` varchar(10) CHARACTER SET gbk DEFAULT NULL,
`b` char(2) CHARACTER SET gbk DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
1 row in set (0.00 sec)
ERROR:
No query specified
(root@localhost) [python]> alter table t add column c varchar(11);
Query OK, 0 rows affected (0.02 sec)
Records: 0 Duplicates: 0 Warnings: 0
(root@localhost) [python]> show create table t\G;
*************************** 1. row ***************************
Table: t
Create Table: CREATE TABLE `t` (
`a` varchar(10) CHARACTER SET gbk DEFAULT NULL,
`b` char(2) CHARACTER SET gbk DEFAULT NULL,
`c` varchar(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
1 row in set (0.00 sec)
ERROR:
No query specified
(root@localhost) [python]> alter table t convert to charset utf8mb4;
Query OK, 0 rows affected (0.04 sec)
Records: 0 Duplicates: 0 Warnings: 0
(root@localhost) [python]> show create table t\G;
*************************** 1. row ***************************
Table: t
Create Table: CREATE TABLE `t` (
`a` varchar(10) DEFAULT NULL,
`b` char(2) DEFAULT NULL,
`c` varchar(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
1 row in set (0.00 sec)
ERROR:
No query specified
3.2.6查看支持的字符集
show charset，Maxlen表示最大的一个字符占用多少个字节
(root@localhost) [python]> show charset;
+----------+---------------------------------+---------------------+--------+
| Charset | Description | Default collation | Maxlen |
+----------+---------------------------------+---------------------+--------+
| big5 | Big5 Traditional Chinese | big5_chinese_ci | 2 |
| dec8 | DEC West European | dec8_swedish_ci | 1 |
| cp850 | DOS West European | cp850_general_ci | 1 |
| hp8 | HP West European | hp8_english_ci | 1 |
| koi8r | KOI8-R Relcom Russian | koi8r_general_ci | 1 |
| latin1 | cp1252 West European | latin1_swedish_ci | 1 |
| latin2 | ISO 8859-2 Central European | latin2_general_ci | 1 |
| swe7 | 7bit Swedish | swe7_swedish_ci | 1 |
| ascii | US ASCII | ascii_general_ci | 1 |
| ujis | EUC-JP Japanese | ujis_japanese_ci | 3 |
| sjis | Shift-JIS Japanese | sjis_japanese_ci | 2 |
| hebrew | ISO 8859-8 Hebrew | hebrew_general_ci | 1 |
| tis620 | TIS620 Thai | tis620_thai_ci | 1 |
| euckr | EUC-KR Korean | euckr_korean_ci | 2 |
| koi8u | KOI8-U Ukrainian | koi8u_general_ci | 1 |
| gb2312 | GB2312 Simplified Chinese | gb2312_chinese_ci | 2 |
| greek | ISO 8859-7 Greek | greek_general_ci | 1 |
| cp1250 | Windows Central European | cp1250_general_ci | 1 |
| gbk | GBK Simplified Chinese | gbk_chinese_ci | 2 |
| latin5 | ISO 8859-9 Turkish | latin5_turkish_ci | 1 |
| armscii8 | ARMSCII-8 Armenian | armscii8_general_ci | 1 |
| utf8 | UTF-8 Unicode | utf8_general_ci | 3 |
| ucs2 | UCS-2 Unicode | ucs2_general_ci | 2 |
| cp866 | DOS Russian | cp866_general_ci | 1 |
| keybcs2 | DOS Kamenicky Czech-Slovak | keybcs2_general_ci | 1 |
| macce | Mac Central European | macce_general_ci | 1 |
| macroman | Mac West European | macroman_general_ci | 1 |
| cp852 | DOS Central European | cp852_general_ci | 1 |
| latin7 | ISO 8859-13 Baltic | latin7_general_ci | 1 |
| utf8mb4 | UTF-8 Unicode | utf8mb4_general_ci | 4 |
| cp1251 | Windows Cyrillic | cp1251_general_ci | 1 |
| utf16 | UTF-16 Unicode | utf16_general_ci | 4 |
| utf16le | UTF-16LE Unicode | utf16le_general_ci | 4 |
| cp1256 | Windows Arabic | cp1256_general_ci | 1 |
| cp1257 | Windows Baltic | cp1257_general_ci | 1 |
| utf32 | UTF-32 Unicode | utf32_general_ci | 4 |
| binary | Binary pseudo charset | binary | 1 |
| geostd8 | GEOSTD8 Georgian | geostd8_general_ci | 1 |
| cp932 | SJIS for Windows Japanese | cp932_japanese_ci | 2 |
| eucjpms | UJIS for Windows Japanese | eucjpms_japanese_ci | 3 |
| gb18030 | China National Standard GB18030 | gb18030_chinese_ci | 4 |
+----------+---------------------------------+---------------------+--------+
41 rows in set (0.00 sec)3.3hex()函数
查看字符的16进制
(root@localhost) [python]> select hex('a');
+----------+
| hex('a') |
+----------+
| 61 |
+----------+
1 row in set (0.00 sec)
(root@localhost) [python]> select hex('ab');
+-----------+
| hex('ab') |
+-----------+
| 6162 |
+-----------+
1 row in set (0.00 sec)
(root@localhost) [python]> select hex('abc');
+------------+
| hex('abc') |
+------------+
| 616263 |
+------------+
1 row in set (0.00 sec)
(root@localhost) [python]> select hex('紫');
+------------+
| hex('紫') |
+------------+
| E7B4AB |
+------------+
1 row in set (0.00 sec)
(root@localhost) [python]> select 0xE7B4AB;
+----------+
| 0xE7B4AB |
+----------+
| 紫 |
+----------+
1 row in set (0.00 sec)
(root@localhost) [python]> insert into t values('aaa',0xE7B4AB,0xE7B4AB);
Query OK, 1 row affected (0.00 sec)
(root@localhost) [python]> select * from t;
+------+------+------+
| a | b | c |
+------+------+------+
| aaa | 紫 | 紫 |
+------+------+------+
1 row in set (0.00 sec)3.4cast()函数
CAST函数用于将某种数据类型的表达式显式转换为另一种数据类型。CAST()函数的参数是一个表达式，它包括用AS关键字分隔的源值和目标数据类型。
语法
CAST(value AS datatype)datatype参数取值
| 值 | 描述 |
| DATE | 将value转换成'YYYY-MM-DD'格式 |
| DATETIME | 将value转换成'YYYY-MM-DD HH：MM：SS'格式 |
| TIME | 将value转换成'HH：MM：SS'格式 |
| CHAR | 将value转换成CHAR(固定长度的字符串)格式 |
| SIGNED | 将value转换成INT(有符号的整数)格式 |
| UNSIGNED | 将value转换成INT(无符号的整数)格式 |
| DECIMAL | 将value转换成FLOAT(浮点数)格式 |
| BINARY | 将value转换成二进制格式 |
(root@localhost) [python]> SELECT CAST('13.6' AS decimal(9,2));
+------------------------------+
| CAST('13.6' AS decimal(9,2)) |
+------------------------------+
| 13.60 |
+------------------------------+
1 row in set (0.00 sec)
(root@localhost) [python]> select cast(123 as char(1));
+----------------------+
| cast(123 as char(1)) |
+----------------------+
| 1 |
+----------------------+
1 row in set, 1 warning (0.00 sec)
(root@localhost) [python]> select cast(123 as char(10));
+-----------------------+
| cast(123 as char(10)) |
+-----------------------+
| 123 |
+-----------------------+
1 row in set (0.00 sec)
(root@localhost) [python]> select cast('a' as char(10));
+-----------------------+
| cast('a' as char(10)) |
+-----------------------+
| a |
+-----------------------+
1 row in set (0.01 sec)
(root@localhost) [python]> select cast('a' as char(10) charset gbk);
+-----------------------------------+
| cast('a' as char(10) charset gbk) |
+-----------------------------------+
| a |
+-----------------------------------+
1 row in set (0.00 sec)
(root@localhost) [python]> select hex(cast('a' as char(10) charset gbk));
+----------------------------------------+
| hex(cast('a' as char(10) charset gbk)) |
+----------------------------------------+
| 61 |
+----------------------------------------+
1 row in set (0.00 sec)
(root@localhost) [python]> select hex('a');
+----------+
| hex('a') |
+----------+
| 61 |
+----------+
1 row in set (0.00 sec)
(root@localhost) [python]> select hex(cast('紫' as char(10) charset gbk));
+------------------------------------------+
| hex(cast('紫' as char(10) charset gbk)) |
+------------------------------------------+
| D7CF |
+------------------------------------------+
1 row in set (0.00 sec)
(root@localhost) [python]> select hex('紫');
+------------+
| hex('紫') |
+------------+
| E7B4AB |
+------------+
1 row in set (0.00 sec)
(root@localhost) [python]> select 0xD7CF;
+--------+
| 0xD7CF |
+--------+
| ؏ |
+--------+
1 row in set (0.00 sec)
(root@localhost) [python]> show create table z\G;
*************************** 1. row ***************************
Table: z
Create Table: CREATE TABLE `z` (
`a` char(1) DEFAULT NULL,
`b` varchar(3) DEFAULT NULL,
`c` binary(1) DEFAULT NULL,
`d` varbinary(3) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
1 row in set (0.00 sec)
ERROR:
No query specified
(root@localhost) [python]> insert into z values('a',0xD7CF,'c',0xD7CF);
ERROR 1366 (HY000): Incorrect string value: '\xD7\xCF' for column 'b' at row 1
(root@localhost) [python]> insert into z values('a',0xE7B4AB,'c',0xD7CF);
Query OK, 1 row affected (0.00 sec)
(root@localhost) [python]> select * from z;
+------+------+------+------+
| a | b | c | d |
+------+------+------+------+
| a | bbb | c | ddd |
| 紫 | bbc | x | ooo |
| a | 紫 | c | ؏ |
+------+------+------+------+
3 rows in set (0.00 sec)从上面看出，varbinary类型不会检测对应的字符是否存在，只会去存16进制的这个值，varchar类型会去检测16进制的值对应的字符是否存在
3.5排序规则collation
(root@localhost) [(none)]> select 'a' = 'a';
+-----------+
| 'a' = 'a' |
+-----------+
| 1 |
+-----------+
1 row in set (0.00 sec)
(root@localhost) [(none)]> select 'a' = 'a ';
+---------------+
| 'a' = 'a ' |
+---------------+
| 1 |
+---------------+
1 row in set (0.00 sec)
(root@localhost) [(none)]> select 'a' = 'A';
+-----------+
| 'a' = 'A' |
+-----------+
| 1 |
+-----------+
1 row in set (0.01 sec)
(root@localhost) [(none)]> select 'a' = 'A ';
+---------------+
| 'a' = 'A ' |
+---------------+
| 1 |
+---------------+
1 row in set (0.00 sec)
(root@localhost) [python]> drop table t;
Query OK, 0 rows affected (0.02 sec)
(root@localhost) [python]> create table t (a char(1),unique key(a));
Query OK, 0 rows affected (0.02 sec)
(root@localhost) [python]> insert into t values('a');
Query OK, 1 row affected (0.00 sec)
(root@localhost) [python]> insert into t values('A');
ERROR 1062 (23000): Duplicate entry 'A' for key 'a'
(root@localhost) [python]> insert into t values('a ');
ERROR 1062 (23000): Duplicate entry 'a' for key 'a'
(root@localhost) [python]> insert into t values('A ');
ERROR 1062 (23000): Duplicate entry 'A' for key 'a'
(root@localhost) [python]> select * from t;
+------+
| a |
+------+
| a |
+------+
1 row in set (0.00 sec)show charset看到的有一列是Default collation，其中utf8mb4字符集对应的排序规则是utf8mb4_general_ci，ci(case insensitive)表示不区分大小写
3.6对于密码的加密，md5()函数
(root@localhost) [python]> drop table t;
Query OK, 0 rows affected (0.01 sec)
(root@localhost) [python]> create table t(password varchar(128));
Query OK, 0 rows affected (0.01 sec)
(root@localhost) [python]> insert into t values('aaa');
Query OK, 1 row affected (0.00 sec)
(root@localhost) [python]> insert into t values('BBB');
Query OK, 1 row affected (0.01 sec)
(root@localhost) [python]> insert into t values(md5('aaa'));
Query OK, 1 row affected (0.01 sec)
(root@localhost) [python]> insert into t values(md5('BBB'));
Query OK, 1 row affected (0.00 sec)
(root@localhost) [python]> select * from t;
+----------------------------------+
| password |
+----------------------------------+
| aaa |
| BBB |
| 47bce5c74f589f4867dbd57e9ca9f808 |
| 2bb225f0ba9a58930757a868ed57d9a3 |
+----------------------------------+
4 rows in set (0.00 sec)
(root@localhost) [python]> insert into t values(md5(concat('aaa','zs')));
Query OK, 1 row affected (0.00 sec)
(root@localhost) [python]> insert into t values(md5(concat('BBB','zs')));
Query OK, 1 row affected (0.01 sec)
(root@localhost) [python]> select * from t;
+----------------------------------+
| password |
+----------------------------------+
| aaa |
| BBB |
| 47bce5c74f589f4867dbd57e9ca9f808 |
| 2bb225f0ba9a58930757a868ed57d9a3 |
| ebf93b07e04f07d5efea104226ce36f5 |
| 5812c79db401f78da7fd2aaf03f9ca97 |
+----------------------------------+
6 rows in set (0.00 sec)密码通过加密存储，一般来说也不区分大小写
强制密码区分大小写
(root@localhost) [python]> create table y (password varchar(128) collate utf8mb4_bin,unique key(password));
Query OK, 0 rows affected (0.01 sec)
(root@localhost) [python]> insert into y values('a');
Query OK, 1 row affected (0.00 sec)
(root@localhost) [python]> insert into y values('A');
Query OK, 1 row affected (0.00 sec)
(root@localhost) [python]> select * from y;
+----------+
| password |
+----------+
| A |
| a |
+----------+
2 rows in set (0.00 sec)3.7upper()和lower()函数
upper()字符串转换成大写，lower()字符串转换成小写
(root@localhost) [python]> select upper('abC');
+--------------+
| upper('abC') |
+--------------+
| ABC |
+--------------+
1 row in set (0.01 sec)
(root@localhost) [python]> select lower('aBC');
+--------------+
| lower('aBC') |
+--------------+
| abc |
+--------------+
1 row in set (0.01 sec)3.8concat()和concat_ws()函数
concat()直接把字符串拼接起来，concat_ws()通过指定的符号把字符串拼接起来
(root@localhost) [python]> select concat('a','b','ccc',123);
+---------------------------+
| concat('a','b','ccc',123) |
+---------------------------+
| abccc123 |
+---------------------------+
1 row in set (0.00 sec)
(root@localhost) [python]> select concat_ws('!','a','b','ccc',123);
+----------------------------------+
| concat_ws('!','a','b','ccc',123) |
+----------------------------------+
| a!b!ccc!123 |
+----------------------------------+
1 row in set (0.00 sec)3.9lpad()和rpad()函数
lpad()左填充，rpad()右填充
(root@localhost) [python]> select lpad('aaa',8,'!');
+-------------------+
| lpad('aaa',8,'!') |
+-------------------+
| !!!!!aaa |
+-------------------+
1 row in set (0.00 sec)
(root@localhost) [python]> select rpad('aaa',8,'!');
+-------------------+
| rpad('aaa',8,'!') |
+-------------------+
| aaa!!!!! |
+-------------------+
1 row in set (0.00 sec)4.enum&set类型
枚举类型常用于性别等distinct的值不多的情况
(root@localhost) [python]> drop table y;
Query OK, 0 rows affected (0.01 sec)
(root@localhost) [python]> create table y (sex enum('male','female'));
Query OK, 0 rows affected (0.01 sec)
(root@localhost) [python]>
(root@localhost) [python]> insert into y values('male');
Query OK, 1 row affected (0.00 sec)
(root@localhost) [python]> insert into y values('male11');
ERROR 1265 (01000): Data truncated for column 'sex' at row 1
(root@localhost) [python]> insert into y values('female');
Query OK, 1 row affected (0.00 sec)
(root@localhost) [python]> insert into y values('zhs');
ERROR 1265 (01000): Data truncated for column 'sex' at row 1
(root@localhost) [python]> select * from y;
+--------+
| sex |
+--------+
| male |
| female |
+--------+
2 rows in set (0.01 sec)5.时间类型
常用日期类型：datetime和timestamp
5.1日期函数
5.1.1now()函数
unix_timestamp(now())是1970-01-01 00:00:00到现在的秒数
(root@localhost) [dbt3]> select now();
+---------------------+
| now() |
+---------------------+
| 2024-03-21 13:21:05 |
+---------------------+
1 row in set (0.00 sec)
(root@localhost) [dbt3]> select unix_timestamp(now());
+-----------------------+
| unix_timestamp(now()) |
+-----------------------+
| 1710998483 |
+-----------------------+
1 row in set (0.00 sec)
(root@localhost) [dbt3]> select timestamp(now());
+---------------------+
| timestamp(now()) |
+---------------------+
| 2024-03-21 13:21:29 |
+---------------------+
1 row in set (0.00 sec)
(root@localhost) [dbt3]> create table z (a datetime,b timestamp);
Query OK, 0 rows affected (0.01 sec)
(root@localhost) [dbt3]> insert into z values(now(),now());
Query OK, 1 row affected (0.00 sec)
(root@localhost) [dbt3]> select * from z;
+---------------------+---------------------+
| a | b |
+---------------------+---------------------+
| 2024-03-21 13:26:50 | 2024-03-21 13:26:50 |
+---------------------+---------------------+
1 row in set (0.00 sec)
(root@localhost) [dbt3]> show variables like 'time_zone';
+---------------+--------+
| Variable_name | Value |
+---------------+--------+
| time_zone | SYSTEM |
+---------------+--------+
1 row in set (0.00 sec)
(root@localhost) [dbt3]> set time_zone = '+0:00';
Query OK, 0 rows affected (0.00 sec)
(root@localhost) [dbt3]> select * from z;
+---------------------+---------------------+
| a | b |
+---------------------+---------------------+
| 2024-03-21 13:26:50 | 2024-03-21 05:26:50 |
+---------------------+---------------------+
1 row in set (0.00 sec)
(root@localhost) [dbt3]> select now(10);
ERROR 1426 (42000): Too-big precision 10 specified for 'now'. Maximum is 6.
(root@localhost) [dbt3]> select now(6);
+----------------------------+
| now(6) |
+----------------------------+
| 2024-03-21 05:29:22.432329 |
+----------------------------+
1 row in set (0.00 sec)
(root@localhost) [dbt3]> select now(3);
+-------------------------+
| now(3) |
+-------------------------+
| 2024-03-21 05:29:36.677 |
+-------------------------+
1 row in set (0.00 sec)5.1.2now()和sysdate()的区别
now()表示该条sql执行开始的时间，sysdate()表示执行到该函数的时间
(root@localhost) [dbt3]> select now(),sysdate(),sleep(4),now(),sysdate();
+---------------------+---------------------+----------+---------------------+---------------------+
| now() | sysdate() | sleep(4) | now() | sysdate() |
+---------------------+---------------------+----------+---------------------+---------------------+
| 2024-03-21 05:34:46 | 2024-03-21 05:34:46 | 0 | 2024-03-21 05:34:46 | 2024-03-21 05:34:50 |
+---------------------+---------------------+----------+---------------------+---------------------+
1 row in set (4.00 sec)
(root@localhost) [dbt3]> select now(6),sysdate(6);
+----------------------------+----------------------------+
| now(6) | sysdate(6) |
+----------------------------+----------------------------+
| 2024-03-21 05:35:58.930067 | 2024-03-21 05:35:58.930234 |
+----------------------------+----------------------------+
1 row in set (0.00 sec)5.1.3date_add()和date_sub()函数
时间加减函数
(root@localhost) [dbt3]> set time_zone='+8:00';
Query OK, 0 rows affected (0.00 sec)
(root@localhost) [dbt3]> select now();
+---------------------+
| now() |
+---------------------+
| 2024-03-21 13:41:15 |
+---------------------+
1 row in set (0.00 sec)
(root@localhost) [dbt3]> select date_add(now(),interval 1 day);
+--------------------------------+
| date_add(now(),interval 1 day) |
+--------------------------------+
| 2024-03-22 13:42:18 |
+--------------------------------+
1 row in set (0.00 sec)
(root@localhost) [dbt3]> select date_add(now(),interval -2 day);
+---------------------------------+
| date_add(now(),interval -2 day) |
+---------------------------------+
| 2024-03-19 13:42:33 |
+---------------------------------+
1 row in set (0.00 sec)
(root@localhost) [dbt3]> select date_add(now(),interval -2 hour);
+----------------------------------+
| date_add(now(),interval -2 hour) |
+----------------------------------+
| 2024-03-21 11:43:06 |
+----------------------------------+
1 row in set (0.00 sec)
(root@localhost) [dbt3]> select date_add(now(),interval -2 minute);
+------------------------------------+
| date_add(now(),interval -2 minute) |
+------------------------------------+
| 2024-03-21 13:41:25 |
+------------------------------------+
1 row in set (0.00 sec)
(root@localhost) [dbt3]> select date_sub(now(),interval 2 day);
+--------------------------------+
| date_sub(now(),interval 2 day) |
+--------------------------------+
| 2024-03-19 14:45:05 |
+--------------------------------+
1 row in set (0.00 sec)
(root@localhost) [dbt3]> select date_sub(now(),interval -2 day);
+---------------------------------+
| date_sub(now(),interval -2 day) |
+---------------------------------+
| 2024-03-23 14:45:10 |
+---------------------------------+
1 row in set (0.00 sec)
(root@localhost) [dbt3]> select date_sub(now(),interval 4 hour);
+---------------------------------+
| date_sub(now(),interval 4 hour) |
+---------------------------------+
| 2024-03-21 10:45:42 |
+---------------------------------+
1 row in set (0.01 sec)5.1.4date_format()函数
语法
DATE_FORMAT(date,format)date 参数是合法的日期，format 规定日期/时间的输出格式。 可用的格式如下：
| 格式 | 描述 |
|---|---|
| %a | 缩写星期名 |
| %b | 缩写月名 |
| %c | 月，数值 |
| %D | 带有英文前缀的月中的天 |
| %d | 月的天，数值(00-31) |
| %e | 月的天，数值(0-31) |
| %f | 微秒 |
| %H | 小时 (00-23) |
| %h | 小时 (01-12) |
| %I | 小时 (01-12) |
| %i | 分钟，数值(00-59) |
| %j | 年的天 (001-366) |
| %k | 小时 (0-23) |
| %l | 小时 (1-12) |
| %M | 月名 |
| %m | 月，数值(00-12) |
| %p | AM 或 PM |
| %r | 时间，12-小时（hh:mm:ss AM 或 PM） |
| %S | 秒(00-59) |
| %s | 秒(00-59) |
| %T | 时间, 24-小时 (hh:mm:ss) |
| %U | 周 (00-53) 星期日是一周的第一天 |
| %u | 周 (00-53) 星期一是一周的第一天 |
| %V | 周 (01-53) 星期日是一周的第一天，与 %X 使用 |
| %v | 周 (01-53) 星期一是一周的第一天，与 %x 使用 |
| %W | 星期名 |
| %w | 周的天 （0=星期日, 6=星期六） |
| %X | 年，其中的星期日是周的第一天，4 位，与 %V 使用 |
| %x | 年，其中的星期一是周的第一天，4 位，与 %v 使用 |
| %Y | 年，4 位 |
| %y | 年，2 位 |
(root@localhost) [dbt3]> select date_format(now(),'%Y/%m/%s %H.%i.%S');
+----------------------------------------+
| date_format(now(),'%Y/%m/%s %H.%i.%S') |
+----------------------------------------+
| 2024/03/25 13.49.25 |
+----------------------------------------+
1 row in set (0.00 sec)
(root@localhost) [dbt3]> select date_format(now(),'%a');
+-------------------------+
| date_format(now(),'%a') |
+-------------------------+
| Thu |
+-------------------------+
1 row in set (0.00 sec)
(root@localhost) [dbt3]> select date_format(now(),'%b');
+-------------------------+
| date_format(now(),'%b') |
+-------------------------+
| Mar |
+-------------------------+
1 row in set (0.00 sec)
(root@localhost) [dbt3]> select date_format(now(),'%W');
+-------------------------+
| date_format(now(),'%W') |
+-------------------------+
| Thursday |
+-------------------------+
1 row in set (0.00 sec)
6.json类型
json类型跟python中的字典类似
(root@localhost) [dbt3]> create table userjson(uid bigint auto_increment primary key,data json);
Query OK, 0 rows affected (0.01 sec)
(root@localhost) [dbt3]> show create table userjson\G
*************************** 1. row ***************************
Table: userjson
Create Table: CREATE TABLE `userjson` (
`uid` bigint(20) NOT NULL AUTO_INCREMENT,
`data` json DEFAULT NULL,
PRIMARY KEY (`uid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
1 row in set (0.00 sec)
(root@localhost) [dbt3]> INSERT INTO userjson(uid,data)VALUES (NULL,'{"name":"David","address": "Shanghai"}');
Query OK, 1 row affected (0.04 sec)
(root@localhost) [dbt3]> INSERT INTO userjson(uid,data)VALUES (NULL,'{"name":"Jim","passport":"E02318883"}');
Query OK, 1 row affected (0.00 sec)
(root@localhost) [dbt3]> select * from userjson;
+-----+------------------------------------------+
| uid | data |
+-----+------------------------------------------+
| 1 | {"name": "David", "address": "Shanghai"} |
| 2 | {"name": "Jim", "passport": "E02318883"} |
+-----+------------------------------------------+
2 rows in set (0.00 sec)6.1json类型相关函数
6.1.1json_extract()函数
(root@localhost) [dbt3]> select uid,json_extract(data,'$.name') from userjson;
+-----+-----------------------------+
| uid | json_extract(data,'$.name') |
+-----+-----------------------------+
| 1 | "David" |
| 2 | "Jim" |
+-----+-----------------------------+
2 rows in set (0.00 sec)
(root@localhost) [dbt3]> select uid,json_unquote(json_extract(data,'$.name')) from userjson;
+-----+-------------------------------------------+
| uid | json_unquote(json_extract(data,'$.name')) |
+-----+-------------------------------------------+
| 1 | David |
| 2 | Jim |
+-----+-------------------------------------------+
2 rows in set (0.00 sec)
(root@localhost) [dbt3]> select uid,data->'$.name' from userjson;
+-----+----------------+
| uid | data->'$.name' |
+-----+----------------+
| 1 | "David" |
| 2 | "Jim" |
+-----+----------------+
2 rows in set (0.00 sec)
(root@localhost) [dbt3]> select uid,data->>'$.name' from userjson;
+-----+-----------------+
| uid | data->>'$.name' |
+-----+-----------------+
| 1 | David |
| 2 | Jim |
+-----+-----------------+
2 rows in set (0.00 sec)
(root@localhost) [dbt3]> select uid,data->>'$.passport' from userjson;
+-----+---------------------+
| uid | data->>'$.passport' |
+-----+---------------------+
| 1 | NULL |
| 2 | E02318883 |
+-----+---------------------+
2 rows in set (0.00 sec)6.1.2json_remove()函数
(root@localhost) [dbt3]> select * from userjson;
+-----+------------------------------------------+
| uid | data |
+-----+------------------------------------------+
| 1 | {"name": "David", "address": "Shanghai"} |
| 2 | {"name": "Jim", "passport": "E02318883"} |
+-----+------------------------------------------+
2 rows in set (0.00 sec)
(root@localhost) [dbt3]> select uid,json_remove(data,'$.name') from userjson;
+-----+----------------------------+
| uid | json_remove(data,'$.name') |
+-----+----------------------------+
| 1 | {"address": "Shanghai"} |
| 2 | {"passport": "E02318883"} |
+-----+----------------------------+
2 rows in set (0.01 sec)
(root@localhost) [dbt3]> select uid,json_remove(data,'$.passport') from userjson;
+-----+------------------------------------------+
| uid | json_remove(data,'$.passport') |
+-----+------------------------------------------+
| 1 | {"name": "David", "address": "Shanghai"} |
| 2 | {"name": "Jim"} |
+-----+------------------------------------------+
2 rows in set (0.00 sec)
