Question

我有两个表：factors和factor_items。 FID是factors的主键和factor_items的外键。

有时我需要在factor表上查看最新的factor_items行及其对应的行。我怎样才能做到这一点？我知道我应该对这些表格进行JOIN查询，但我对latest row(max FID)没有任何想法：

SELECT * FROM factors INNER JOIN factor_items ON factors.FID = factor_items.FID;

Answer 1

如果您包含WHERE条件以检查最大ID，例如

，该怎么办？

SELECT * FROM factors 
INNER JOIN factor_items 
ON factors.FID = factor_items.FID
WHERE factors.FID IN ( select max(FID) from factors );

（OR）使用order by和limit子句

SELECT * FROM factors 
INNER JOIN factor_items 
ON factors.FID = factor_items.FID
order by factors.FID desc 
limit 100;

Answer 2

希望这会帮助你，尝试一下

SELECT * FROM factors 
INNER JOIN factor_items ON factors.FID = factor_items.FID 
WHERE factors.FID IN (select FID from factors  ORDER BY FID desc limit 1);

Mysql - 如何改进此查询？

2 个答案: