MySQL 手动 id 增量

Question

我有以下疑问：

SET @count = 0;
UPDATE `batch_b`
SET `batch_b`.`printid` = @count:=@count+1;
ORDER BY postal_zone, country, airmail,company;

PrintID 是一个整数，默认值为 0。这不是主键。 当我运行查询时，我希望它给出一次增量值，但它只返回 NULL。

Answer 1

它在用括号包裹增量值后工作。谢谢！

Set @counter := 0;
UPDATE `batch_b`
SET `batch_b`.`printid` = (@counter:=@counter+1)
ORDER BY postal_zone, country, airmail,company;