MySQL nested use

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1. subquery of select statement:

Syntax: Select... from table 1 where column 1 =
(Select... from... where ....)

 

2. SELECT statement Table query

Syntax: Select... from (Select...) as temp_table where...

Note: The column names cannot be repeated! Some people will see:#1060-duplicate column name 'column name' error. This indicates that the column name is repeated.

Solution: Remove a column name.

PS: this is a little different from the MSSQL alias,

Select * from (select * from a) B

 

3. query the conditional association relationship:
Syntax: easy to view my indentationCode

Select col1 from T1 as

Where a. col1 = (select col1 from B as
Where a. col1 = (select col1 from C
Where a. col2 = C. col1

)

);

 

4. Select (select S1 from T2) from T1;
5. Select (select S2 from T1 );