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What should I pay attention to when using the sleep function in MySQL? Many novices are not very clear about this. In order to help you solve this problem, the following editor will explain it in detail. People with this need can come and learn. I hope you can gain something.

Preface

The system function sleep in MySQL, which is not widely used in practical application, is generally used for experimental testing. Yesterday, during the test, I accidentally found a special phenomenon of the sleep function. If you use the sleep function in a query statement, the sleep time is related to the records returned.

As shown in the following test:

Mysql > create table test (id int); Query OK, 0 rows affected (0.03 sec) mysql > select *, sleep (6) from test;Empty set (0.00 sec) mysql > insert into test values (1); Query OK, 1 row affected (0.00 sec) mysql > select *, sleep (6) from test +-+-+ | id | sleep (6) | +-+-+ | 1 | 0 | +-+ 1 row in set (6.00 sec) mysql > insert into test value (2); Query OK, 1 row affected (0.01 sec) mysql > select *, sleep (6) from test +-+-+ | id | sleep (6) | +-+-+ | 1 | 0 | 2 | 0 | +-+-+ 2 rows in set (12.00 sec)

Test summary:

If, select *, sleep (n) from table, if the table record is empty, it will not sleep, if the table records one, then the dormancy time is 1 sleep n, if the table record is 2, the sleep time is: 2 sleep n. And so on.

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