How does mysql obtain the total number of rows of group by records? mysqlgroup

How does mysql obtain the total number of rows of group by records? mysqlgroup

This article describes how mysql can obtain the total number of group by records. The specific method is analyzed as follows:

In general, mysql can obtain the total number of record groups for a field within the group by, but cannot count the number of records in the group.

In mysql, you can use SQL _CALC_FOUND_ROWS to obtain the number of queried rows, which is written in many paging programs as follows:
Copy codeThe Code is as follows: select count (*) from 'table' WHERE ......;
Check the total number of qualified records:
Copy codeThe Code is as follows: SELECT * FROM 'table' WHERE... limit M, N;
To query the data to be displayed on the page, you can change the statement:
Copy codeThe Code is as follows: SELECT SQL _CALC_FOUND_ROWS * FROM 'table' WHERE... limit M, N;
SELECT FOUND_ROWS ();
Therefore, the following functions can be used with the SQL _CALC_FOUND_ROWS and FOUND_ROWS () functions provided by mysql:
Copy codeThe Code is as follows: SELECT SQL _CALC_FOUND_ROWS t3.id, a, bunch, of, other, stuff FROM t1, t2, t3 WHERE (associate t1, t2, and t3 with each other) GROUPBY t3.id LIMIT 10, 20 SELECT FOUND_ROWS () as count;
Use the preceding two statements to complete the total number of records that meet the requirements of group.

Supplement:

Simple use of group:
Copy codeThe Code is as follows: 'select column_id, count (*) as count FROM my_table group by column_id ';

I hope this article will help you design MySQL database programs.

How to count the number of records after the mysql group, count after gourp

Select count (*) from
(SELECT count (*) FROM table name WHERE condition group by id);

How can I obtain the number of rows of data returned by the MYSQL database in PHP?

Mysql_num_rows () or select count (*) from table;