通过MySql中的变量设置AUTO_INCREMENT值 [英] Set AUTO_INCREMENT value through variable in MySql

问题描述

我有一个带有auto_increment列的表.我将列的最后一个值保存在另一个名为ids_tbl的表中，当mysql重新启动时，从ids_tbl中读取该值并重新设置AUTO_INCREMENT值. 如果我这样做:

I have a table with an auto_increment column. I save the last value of the column in another table called ids_tbl, and when mysql restarts, read the value from ids_tbl and re-set the AUTO_INCREMENT value. If I do this:

alter table outgoing_tbl auto_increment=500; 

有效

但是，如果我这样做

select @max_id:= max_id FROM ids_tbl;
alter table outgoing_tbl auto_increment=@max_id; 

或者如果我这样做:

select @max_id:= max_id FROM ids_tbl;
alter table outgoing_tbl auto_increment=(select @max_id); 

然后它不起作用，如何通过变量设置自动增量值?

Then it does not work, how do I set the auto increment value throgh a variable?

推荐答案

使用以下代码.一切正常. 并遵循MySQL准备的语句 https://dev .mysql.com/doc/refman/5.7/en/sql-syntax-prepared-statements.html

Use the below code. This is working fine. And follow the MySQL prepared statement https://dev.mysql.com/doc/refman/5.7/en/sql-syntax-prepared-statements.html

SET @max_id = (SELECT MAX(id) FROM `ids_tbl` );
SET @sql = CONCAT('ALTER TABLE `outgoing_tbl` AUTO_INCREMENT = ', @max_id);
PREPARE st FROM @sql;
EXECUTE st;

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