MySQL Benchmark

问题

I am trying to use MySQL benchmark to test some queries. But, I am running to an error.

SELECT benchmark (10000, (select title from user));

and in return I get this error;

ERROR 1242 (21000): Subquery returns more than 1 row

Does anyone know how to benchmark a query?

Thanks

回答1:

select title from user

This returns multiple rows, which won't work.

Refer to this link: http://dev.mysql.com/doc/refman/5.0/en/information-functions.html#function_benchmark

The expression you pass must return a scalar result.

You need to change the query such that it returns a single row: ex:

select title from user where user_name = 'some_user'

回答2:

you can use the mysqlslap utility to benchmark queries, see: http://dev.mysql.com/doc/refman/5.1/en/mysqlslap.html

回答3:

From http://dev.mysql.com/doc/refman/5.0/en/information-functions.html#function_benchmark

Only scalar expressions can be used. Although the expression can be a subquery, it must return a single column and at most a single row. For example, BENCHMARK(10, (SELECT * FROM t)) will fail if the table t has more than one column or more than one row.

Try

SELECT BENCHMARK(10000, (SELECT title FROM user LIMIT 1));

来源：https://stackoverflow.com/questions/1971150/mysql-benchmark