Mysql limit optimization methods and detailed descriptions (1/3)

The LIMIT clause can be used to force the SELECT statement to return the specified number of records. LIMIT accepts one or two numeric parameters. The parameter must be an integer constant. If two parameters are specified, the first parameter specifies the offset of the first returned record row, and the second parameter specifies the maximum number of returned record rows. The offset of the initial record row is 0 (not 1 ):

Select * from table limit [offset,] rows | rows offset

The limit clause can be used to force the select statement to return the specified number of records. Limit accepts one or two numeric parameters. The parameter must be an integer constant. If two parameters are specified, the first parameter specifies the offset of the first returned record row, and the second parameter specifies the maximum number of returned record rows. The offset of the initial record row is 0 rather than 1. To be compatible with postgresql, the mysql tutorial also supports Syntax: limit # offset #.

Mysql> select * from table limit 5, 10; // retrieves records from 6 to 15 rows.

// To retrieve all record rows from an offset to the end of the record set, you can specify the second parameter-1:

Mysql> select * from table limit 95,-1; // retrieves 96-last records.

// If only one parameter is specified, it indicates the maximum number of record rows returned:

Mysql> select * from table limit 5; // retrieve the first five record rows

// In other words, limit n is equivalent to limit 0, n.

Note the differences between limit 10 and limit 9 and 1:

For example:

1.

 

 

Select * from cyclopedia where id> = (
Select max (id) from (
Select id from cyclopedia order by id limit 90001
) As tmp
) Limit 100;

 

 

2.

 

Select * from cyclopedia where id> = (
Select max (id) from (
Select id from cyclopedia order by id limit 90000,1
) As tmp
) Limit 100;

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