A detailed explanation of join syntax in SQL

Refer to the following two blog posts:

The first is the SQL syntax: INNER join on, left join on, right join on detailed usage method

The meaning and usage of the inner join, the left JOIN, the right join.

The second one is the left outer join,inner join,right outer join usage in SQL

The mathematical principles behind relational operations, as well as more types of connection operations are mentioned:

Inner join-Cartesian product,

Left OUTER JOIN,

Right outer JOIN,

Full outer JOIN,

Cross Join-Cartesian product,

self-connection;

It is also mentioned that the conditional keyword on (as a keyword for join) is sometimes the same as where (the keyword for select), and see Select * * * * FROM table 1 t1, table 2 T2 where * * * Such statements are actually early connection syntax ~

A detailed explanation of join syntax in SQL