now , I need to select a table per minute. 1. the table struture: ----------------------------------------------------------------- CREATE TABLE `table_code` ( `timestamp` timestamp NULL default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP, `code` decimal(5,0) NOT NULL default '0', PRIMARY KEY (`stock_code`) ) ----------------------------------------------------------------- 2. there is a trigger will insert data into the table `table_code` the trigger is like: ----------------------------------------------------------------- if .... then insert into table_code.... end if; ----------------------------------------------------------------- 3. I need to select the table 'table_code' per minute,and the sql is like : select code from table_code;
now, the problem is: in normally,the sql executed very fast (0.5-1 second), but sometimes, it will take more than 3 minutes. I don't know why? how to find the cause?