mysql第四篇--SQL逻辑查询语句执行顺序

一.SQL语句定义顺序

SELECT DISTINCT <select_list>
FROM <left_table>
<join_type> JOIN <right_table>
ON <join_condition>
WHERE <where_condition>
GROUP BY <group_by_list>
HAVING <having_condition>
ORDER BY <order_by_condition>
LIMIT <limit_number>

二.准备测试

1. 新建一个测试数据库TestDB;

CREATE DATABASE TestDB DEFAULT charset utf8;

 

2.创建测试表table1和table2;　　

CREATE TABLE table1(
     customer_id VARCHAR(10) NOT NULL,
     city VARCHAR(10) NOT NULL,
     PRIMARY KEY(customer_id)
 )ENGINE=INNODB DEFAULT CHARSET=UTF8;


 CREATE TABLE table2(
     order_id INT NOT NULL auto_increment,
     customer_id VARCHAR(10),
     PRIMARY KEY(order_id)
 )ENGINE=INNODB DEFAULT CHARSET=UTF8;

创建表