文章目录

• • • 1 . Introduction
    • 2. Detail
    • • 2.1 sql query with many tables
      • 2.2 Sub query

1 . Introduction

Sql query with many tables is oftern used by us. In the conetent there is sql query with many tables and sub query.

2. Detail

2.1 sql query with many tables

Inner join: Share relation fields.
left join : The left table is main table.And all fields are displayed in the left tables.
right join: The right table is main table.And all fields are displayed in the right tables.
There are two relations in the three table.

2.2 Sub query

There is related query and not related query.