select * from employees where emp_no = '10002' ;
select * from salaries where emp_no = '10002' ;
+--------+------------+------------+-----------+--------+------------+
| emp_no | birth_date | first_name | last_name | gender | hire_date |
+--------+------------+------------+-----------+--------+------------+
| 10002 | 1964-06-02 | Bezalel | Simmel | F | 1985-11-21 |
+--------+------------+------------+-----------+--------+------------+
1 row in set (0.00 sec)
+--------+--------+------------+------------+
| emp_no | salary | from_date | to_date |
+--------+--------+------------+------------+
| 10002 | 65828 | 1996-08-03 | 1997-08-03 |
| 10002 | 65909 | 1997-08-03 | 1998-08-03 |
| 10002 | 67534 | 1998-08-03 | 1999-08-03 |
| 10002 | 69366 | 1999-08-03 | 2000-08-02 |
| 10002 | 71963 | 2000-08-02 | 2001-08-02 |
| 10002 | 72527 | 2001-08-02 | 9999-01-01 |
+--------+--------+------------+------------+
6 rows in set (0.00 sec)
select
now ( ) as '查询时间' ,
a. emp_no as '员工编号' ,
concat( b. last_name, ' ' , b. first_name) as '姓名' ,
concat_ws( ':' , b. last_name, b. first_name) as '姓名(字符串拼接)' ,
replace ( b. last_name, 'Simmel' , 'Simmel-齐美尔' ) as '姓(替换)' ,
ucase ( b. last_name) as '姓(大写)' ,
upper( b. last_name) as '姓(大写)' ,
mid ( b. last_name, 1 , 1 ) as '姓(首字母-从索引1开始计数)' ,
replace ( b. first_name, 'Bezalel' , '贝扎雷-Bezalel' ) as '名(替换)' ,
lcase ( b. first_name) as '名(小写)' ,
lower( b. first_name) as '名(小写)' ,
length( b. first_name) as '名(长度)' ,
field( 'Bezalel' , b. last_name, b. first_name) as 'Bezalel(名的索引)' ,
trim( ' 做个人吧 ' ) as '去除前后空格' ,
b. gender as '性别' ,
repeat ( b. gender, 10 ) as '复制10分性别' ,
if ( b. gender = 'F' , '女' , '男' ) as '性别(三元运算)' ,
case
when b. gender = 'F' then '女'
when b. gender = 'M' then '男'
else '变态' end
as '性别(三元运算)' ,
isnull( b. gender) as '是否为变态(isnull)' ,
isnull( null ) as '是否为null(isnull)' ,
ifnull( b. gender, '变态' ) as '是否为变态(ifnull)' ,
ifnull( null , 'null' ) as '是否为null(ifnull)' ,
coalesce ( b. gender, '变态' ) as '是否为变态(coalesce)' ,
coalesce ( null , 'null' ) as '是否为null(coalesce)' ,
b. birth_date as '出生日期' ,
b. hire_date as '雇佣日期' ,
left ( b. birth_date, 4 ) as '年(从左侧截取4个字符)' ,
substring( b. birth_date, 6 , 2 ) as '月(从左侧6处开始截取2个字符)' ,
substr( b. birth_date, 6 , 2 ) as '月(从左侧6处开始截取2个字符)' ,
right ( b. birth_date, 2 ) as '日(从右侧截取2个字符)' ,
substring_index( 'www.baidu.com' , '.' , - 2 ) as '以.分割字符串逆向截取两个元素' ,
locate( '.' , 'baidu.com.cn' ) as '.第一次出现的位置' ,
group_concat( a. salary separator ';' ) as '薪资' ,
count ( a. salary) as '数量' ,
avg ( a. salary) as '平均值' ,
round ( avg ( a. salary) ) as '四舍五入(平均值)' ,
format ( avg ( a. salary) , 0 ) as '平均值(格式化)' ,
format ( avg ( a. salary) , 10 ) as '平均值(格式化)' ,
sum ( a. salary) as '总和' ,
max ( a. salary) as '最大值' ,
min ( a. salary) as '最小值' ,
sqrt( sum ( a. salary) ) as '总和平方根' ,
rand( ) * 100 as '随机数(0到1 * 100)' ,
floor( 1.2345 ) as '返回不大于参数的最大整数' ,
floor( - 1.2345 ) as '返回不大于参数的最大整数' ,
ceiling( 1.2345 ) as '返回不小于参数的最小整数' ,
ceiling( - 1.2345 ) as '返回不小于参数的最小整数' ,
abs( - 2 ) as '绝对值' ,
5 div 2 as '5/2' ,
mod ( 3 , 2 ) as '3%2' ,
mod ( 2 , 3 ) as '2%3' ,
pow( 2 , 3 ) as '2^3' ,
power( 2 , 3 ) as '2^3' ,
pi( ) as '圆周率' ,
cos( pi( ) ) as 'cos(余弦)' ,
sin( pi( ) ) as 'sin(正弦)' ,
tan( pi( ) ) as 'tan(正切)' ,
acos( 1 ) as 'acos(反余弦)' ,
asin( 1 ) as 'asin(反正弦)' ,
atan( 1 ) as 'atan(反正切)' ,
least( 2 , 1 , 4 , 0 , 1 ) as '返回最小值' ,
greatest( 2 , 1 , 4 , 0 , 1 ) as '返回最大值' ,
degrees( pi( ) ) as '从弧度转换为角度' ,
radians( 180 ) as '从角度转换为弧度' ,
truncate ( 0.123456789 , 5 ) as '保留有效数字(不四舍五入)' ,
sign( - 100 ) as '参数符号' ,
sign( 0 ) as '参数符号' ,
sign( 100 ) as '参数符号'
from
( select * from salaries where emp_no = '10002' ) as a
inner join
employees as b
on
a. emp_no = b. emp_no
group by
a. emp_no;
select date_add( '2023-01-01' , interval 7 day ) as '增加7天' ,
adddate( '2023-01-01' , interval 7 hour ) as '增加7小时' ,
adddate( '2023-01-01' , interval 7 minute ) as '增加7分钟' ,
adddate( '2023-01-01' , interval '07-01' year_month) as '增加7年1月' ,
date_sub( '2023-01-20' , interval 7 day ) as '减去7天' ,
subdate( '2023-01-20' , interval 7 hour ) as '减去7小时' ,
addtime( '00:00:00' , '01:00:00' ) as '增加1小时' ,
subtime( '00:00:00' , '07:07:07' ) as '减去7小时7分7秒' ,
convert_tz( '2023-01-01 01:01:01' , '+8:00' , '+10:00' ) as '从+8:00时区修改为+9:00时区' ,
curdate( ) as '返回当前日期' ,
current_date ( ) as '返回当前日期' ,
current_date as '返回当前日期' ,
curtime( ) as '返回当前时间' ,
current_time ( ) as '返回当前时间' ,
current_time as '返回当前时间' ,
now ( ) as '返回当前日期时间' ,
localtime( ) as '返回当前日期时间' ,
localtime as '返回当前日期时间' ,
localtimestamp( ) as '返回当前日期时间' ,
localtimestamp as '返回当前日期时间' ,
current_timestamp ( ) as '返回当前日期时间' ,
current_timestamp as '返回当前日期时间' ,
date_format( now ( ) , '%Y(4位年) - %y(2位年)' ) as '年' ,
date ( now ( ) ) as '从 date 或者 datetime 表达式中提取出日期部分' ,
datediff( '2023-01-01 10:10:10' , '1997-02-11 07:01:01' ) as '日期相减得出天' ,
day ( '2020-01-31' ) as '返回某天是当月的第几天(1-31)' ,
dayofmonth( '2020-02-31' ) as '返回某天是当月的第几天(1-31)' ,
dayname( '2020-01-31' ) as '返回某天在用星期中的名称' ,
dayofweek( '2020-01-31' ) as '返回某天是该星期的第几天' ,
dayofyear( '2020-02-21' ) as '返回某天是一年中的第几天(1-366)' ,
extract( year_month from now ( ) ) as '提取日期中的某一部分' ,
from_days( 366 ) as '将天数转换为日期' ,
from_unixtime( 1580436610 ) as '将某个 UNIX 时间戳格式化为日期' ,
unix_timestamp( '2020-01-31 10:10:10' ) as '将某个日期格式化为 UNIX 时间戳' ,
last_day( '2020-01-10 10:10:10' ) as '返回参数日期所在月份的最后一天' ,
makedate( 2023 , 100 ) as '利用年份和某天在该年所处的天数来创建日期' ,
maketime( 112 , 50 , 50 ) as '根据小时，分钟和秒值创建并返回时间值' ,
year ( now ( ) ) as '由参数返回年' ,
month ( now ( ) ) as '由参数返回月份' ,
monthname( now ( ) ) as '由参数返回月份名称' ,
yearweek( now ( ) ) as '由参数返回年周数' ,
weekofyear( now ( ) ) as '由参数返回周数' ,
weekday( now ( ) ) + 1 as '返回星期几' ,
week( now ( ) ) as '由参数返回周数' ,
time ( now ( ) ) as '时间' ,
hour ( now ( ) ) as '由参数返回小时' ,
minute ( now ( ) ) as '由参数返回分钟' ,
second ( now ( ) ) as '由参数返回秒' ,
microsecond( now ( ) ) as '由参数返回毫秒' ,
to_days( now ( ) ) as '将日期参数转换为天数' ,
utc_date( ) as '返回当前 UTC 日期' ,
utc_time( ) as '返回当前 UTC 时间' ,
utc_timestamp( ) as '返回当前 UTC 日期和时间' ,
quarter( now ( ) ) as '返回日期参数所在的季度' ,
sec_to_time( 100000 ) as '将秒数转换为 ''HH:MM:SS'' 格式' ,
str_to_date( '2020-01-10 10:20:30' , '%Y-%m-%d %H:%i:%s' ) as '将字符串转换为日期数据' ,
sysdate( ) as '返回函数执行的时的时刻' ,
time_format( '20201010 101010' , '%Y-%m-%d %H:%i:%s' ) as '格式化时间' ,
time_to_sec( '10:10:10' ) as '将时间参数转换为秒数' ,
timediff( '2020-01-01 10:10:10' , '2023-01-01 20:20:20' ) as '将两个时间相减返回时分秒' ,
period_add( 201808 , 2 ) as '参数年月加上参数月' ,
period_diff( 201808 , 201810 ) as '返回两个年月格式的日期数据之间的月份数' ,
timestampadd( day , 3 , now ( ) ) as '3天以后的日期时间' ,
timestampdiff( second , '2023-07-21 10:10:10' , '2023-07-20 01:01:01' ) as '两个日期时间相减' ,
timestamp ( '2020-01-01' ) as '返回参数的日期时间' ,
timestamp ( now ( ) , '3:00:00' ) as '返回参数日期时间加上时间' ;
