1.购买表
Id user pur_type
----------------------
1 408 5-12
2 408 5-12
3 222 1-11
4 222 5-12
5 408 1-11
6 408 1-11
2。货物表
Id parts days
-----------------
1 1-11 50
2 5-12 40
我实现了这样的查询
SELECT p1.id, p1.user, p1.pur_type, g.parts, g.days
FROM purchase p1
INNER JOIN goods g ON p1.pur_type = g.parts
LEFT JOIN goods p2 ON ( p1.pur_type= p2.pur_type
AND p1.id < p2.id )
WHERE p2.id IS NULL
结果只是每个pur_type的最后一条记录
Id user pur_type parts days
---------------------------------
4 222 5-12 5-12 40
6 408 1-11 1-11 50
如何从一个特定用户的每个purchase
的{{1}}表中获取最后一条记录?
例如对于用户408需要结果:
pur_type
结果说明:
用户408的最后记录fot Id user parts days
-------------------------
2 408 5-12 40
6 408 1-11 50
5-12是part
= 2
用户408的id
1-11的最后记录是part
= 6
答案 0 :(得分:0)
SELECT a.*, c.* -- select columns youw ant
FROM Purchase a
INNER JOIN
(
SELECT user, MAX(ID) max_ID
FROM Purchase
GROUP BY user, pur_type
) b ON a.user = b.user AND
a.ID = b.max_ID
INNER JOIN goods c
ON a.pur_type = c.parts
WHERE a.USER = 408
为了获得更好的效果,请在表parts
上的goods
列上添加一个INDEX以及pur_type
答案 1 :(得分:0)
对现有查询的简单修改:
SELECT p1.id, p1.user, p1.pur_type, g.parts, g.days
FROM purchase p1
INNER JOIN goods g ON p1.pur_type = g.parts
LEFT JOIN purchase p2
ON ( p1.pur_type= p2.pur_type AND p1.id < p2.id AND p1.user=p2.user)
WHERE p2.id IS NULL and p1.user = 408