一、准备工作

执行以下SQL脚本，作用是：在study数据库中创建products，并向表中插入14条具体数据

#######################
# Create products table
#######################
USE `study`;

CREATE TABLE products
(
  prod_id    char(10)      NOT NULL,
  vend_id    int           NOT NULL ,
  prod_name  char(255)     NOT NULL ,
  prod_price decimal(8,2)  NOT NULL ,
  prod_desc  text          NULL ,
  PRIMARY KEY(prod_id)
) ENGINE=InnoDB;

#########################
# Populate products table
#########################
INSERT INTO products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('ANV01', 1001, '.5 ton anvil', 5.99, '.5 ton anvil, black, complete with handy hook');
INSERT INTO products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('ANV02', 1001, '1 ton anvil', 9.99, '1 ton anvil, black, complete with handy hook and carrying case');
INSERT INTO products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('ANV03', 1001, '2 ton anvil', 14.99, '2 ton anvil, black, complete with handy hook and carrying case');
INSERT INTO products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('OL1', 1002, 'Oil can', 8.99, 'Oil can, red');
INSERT INTO products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('FU1', 1002, 'Fuses', 3.42, '1 dozen, extra long');
INSERT INTO products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('SLING', 1003, 'Sling', 4.49, 'Sling, one size fits all');
INSERT INTO products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('TNT1', 1003, 'TNT (1 stick)', 2.50, 'TNT, red, single stick');
INSERT INTO products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('TNT2', 1003, 'TNT (5 sticks)', 10, 'TNT, red, pack of 10 sticks');
INSERT INTO products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('FB', 1003, 'Bird seed', 10, 'Large bag (suitable for road runners)');
INSERT INTO products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('FC', 1003, 'Carrots', 2.50, 'Carrots (rabbit hunting season only)');
INSERT INTO products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('SAFE', 1003, 'Safe', 50, 'Safe with combination lock');
INSERT INTO products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('DTNTR', 1003, 'Detonator', 13, 'Detonator (plunger powered), fuses not included');
INSERT INTO products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('JP1000', 1005, 'JetPack 1000', 35, 'JetPack 1000, intended for single use');
INSERT INTO products(prod_id, vend_id, prod_name, prod_price, prod_desc)
VALUES('JP2000', 1005, 'JetPack 2000', 55, 'JetPack 2000, multi-use')

在这里插入图片描述
这样我们就得到了一张如下图所示的表数据

新增一个SQL编辑页面后面使用

二、基本的select查询语句

接下来我们将使用上面创建的products表来学习一些基本的select查询语句

2.1、检索单个列

SELECT 
	prod_name 
FROM 
	products;

上述语句利用SELECT语句从products表中检索prod_name列的所有行数据。
在这里插入图片描述

2.2、检索多个列

SELECT 
	prod_id, prod_name, prod_price 
FROM 
	products;

2.3、检索所有列

用星号（*）通配符检索所有列

SELECT 
	* 
FROM 
	products;

2.4、检索不同的行——使用关键字`DISTINCT`去除重复行

SELECT DISTINCT
    vend_id
FROM
    products;

2.5、限制检索行数——使用关键字`LIMIT`限制返回结果的行数

SELECT 
	prod_name 
FROM 
	products 
LIMIT 0，5;-- 从第0行开始往后检索5条数据

三、使用完全限定

3.1、完全限定数据库

####################之前是不限定的表名写法####################
SELECT 
    prod_name, prod_price
FROM
    products
####################使用完全限定数据库写法####################
SELECT 
    prod_name, prod_price
FROM
    study.products;	-- 限定使用的是数据库study

3.2、完全限定表名

####################之前是不限定的表名写法####################
SELECT 
    prod_name, prod_price
FROM
    products
####################使用完全限定表名写法####################
SELECT 
    products.prod_name, products.prod_price -- 限定使用的是表products
FROM
    products;

3.3、同时限定数据库和表

####################之前是不限定的表名写法####################
SELECT 
    prod_name, prod_price
FROM
    products
####################使用完全限定表名写法####################
SELECT 
    products.prod_name, products.prod_price -- 限定使用的是表products
FROM
    study.products;	-- 限定使用的是数据库study