我使用以下查询从子集中为每个ID1-ID2对在时间上具有最小距离(YEAR和MMDD字段)的记录随机绘制一行, 。修复mysql查询以返回子组内的随机行
CREATE TABLE temp4 AS
SELECT *
FROM temp3
GROUP BY ID1, ID2
ORDER BY DATEDIFF(CONCAT(YEAR,'-',LEFT(MMDD,2),'-',RIGHT(MMDD,2)), CONCAT(ID3_YEAR,'-',LEFT(ID3_MMDD,2),'-',RIGHT(ID3_MMDD,2))) ASC, RAND()
LIMIT 0, 1;
从前面的问题我已经张贴在这里,这是表的样子
ID1 ID2 YEAR MMDD ID3 YEAR_ID3 MMDD_ID3
---------------------------------------
1 2 1991 0821 55 1991 0822
1 2 1991 0821 57 1991 0822
1 2 1991 0821 88 1992 0101
1 3 1990 0131 89 2000 0202
1 3 1990 0131 89 2001 0102
FOR EACH ID1,ID2对,我需要
选择ID3时间上的最小距离(YEAR字段和MMDD字段,即我需要比较YEAR和MMDD与YEAR_ID3和MMDD_ID3)
如果多于一个ID3满足最低要求(即,他们都有相同的YEAR_ID3和MMDD_ID3),我需要随机选择一个。
在上面的例子中,查询应该返回
1,2,1991,0821,55 (OR 1,2,1991,0821,57 - ACCORDING TO THE RANDOM DRAW)
1,3,1990,0131,89
我上面粘贴只返回一行ONE ... :(
莫名其妙地出现了一个很好的解决方案在下面评论区张贴OMG ......但它消失了?!?!?
我在这里把它粘贴
DROP TABLE IF EXISTS temp4;
CREATE TABLE temp4 AS
SELECT x.id1,
x.id2,
x.YEAR,
x.MMDD,
x.id3,
x.id3_YEAR,
x.id3_MMDD
FROM (SELECT t.*,
ABS(DATEDIFF(CONCAT(CAST(t.id3_YEAR AS CHAR(4)),'-', LEFT(t.id3_MMDD,2),'-',RIGHT(t.id3_MMDD,2)),
CONCAT(CAST(t.YEAR AS CHAR(4)),'-', LEFT(t.MMDD,2),'-',RIGHT(t.MMDD,2)))) AS diff,
CASE
WHEN @id1 = t.id1 AND @id2 = t.id2 THEN @rownum := @rownum + 1
ELSE @rownum := 1
END AS rk,
@id1 := t.id1,
@id2 := t.id2
FROM temp3 t
JOIN (SELECT @rownum := 0, @id1 := 0, @id2 := 0) r
ORDER BY t.id1, t.id2, diff, RAND()) x
WHERE x.rk = 1;
我在这里粘贴一个测试表
DROP TABLE IF EXISTS `temp3`;
CREATE TABLE IF NOT EXISTS `temp3` (
`id1` char(7) NOT NULL,
`id2` char(7) NOT NULL,
`YEAR` year(4) NOT NULL,
`MMDD` char(4) NOT NULL,
`id3` char(7) NOT NULL,
`id3_YEAR` year(4) NOT NULL,
`id3_MMDD` char(4) NOT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1;
INSERT INTO `temp3` VALUES('1', '2', 1992, '0107', '55', 1991, '0528');
INSERT INTO `temp3` VALUES('1', '2', 1992, '0107', '57', 1991, '0701');
INSERT INTO `temp3` VALUES('1', '3', 1992, '0107', '88', 2000, '0101');
INSERT INTO `temp3` VALUES('1', '3', 1992, '0107', '44', 2000, '0101');
是否有原因,为什么你不使用'DATE'字段而不是'YEAR'和'MMDD'在这里? – Hammerite 2010-09-26 01:24:05
是的,这就是数据来的方式(表格非常庞大 - 6M行)。如果你认为它很有用,我很乐意为你添加一个新的专栏... – Cat 2010-09-26 01:25:27
OMG小马,你的答案消失了吗? – Cat 2010-09-26 04:38:07