我正在尝试使用嵌套查询组合 2 个查询。 第一个是这样的:
SELECT DISTINCT( de.MCH_CODE) AS Mach, md.MAT_CODE as ShortenCode, de.TIME as start_time
FROM table1 AS de
JOIN table1table2 AS md
ON de.subcode= md.subcode
WHERE de.ev = '123' AND de.time > '2017-11-14 07:00' and de.side = 'R' AND de.end IS NULL AND de.Subcat = 'STOP'
ORDER BY de.time
生成结果
Mach ShortenCode Tme
Mach1 451 2017-12-25 08:25
Mach2 854 2017-12-25 08:25
所以 451 在 Mach1 上。棘手的部分是,对于 ShortenCode,我想显示它所在的前一个 Mach。 它会是这样的:
SELECT distinct de.MCH_CODE FROM table1 AS de
join table2 as md
ON de.subcode = md.subcode
WHERE de.ShortenCode = 'the ones displayed in the first query'
如何通过子查询获取:
Mach ShortenCode Tme Mach(Previous)
Mach1 451 2017-12-25 08:25 Mach4
Mach2 854 2017-12-25 08:25 Mach5
基本上 Mach 列有 Mach1,Mach2,还有 Mach4 和 Mach5。 我试过这个但没有成功:
SELECT t1.Mach, t1.ShortenCode, t1.start_time, t2.PreviousMach
FROM( SELECT DISTINCT( de.MCH_CODE) AS Mach, md.MAT_CODE as ShortenCode, de.TIME as start_time, mch_
FROM table1 AS de
JOIN table1table2 AS md
ON de.subcode= md.subcode
WHERE de.ev = '123' AND de.time > '2017-11-14 07:00' and de.side = 'R' AND de.end IS NULL AND de.Subcat = 'STOP'
ORDER BY de.time
) t1
join
( SELECT distinct de.MCH_CODE FROM table1 AS de
join table2 as md
ON de.subcode = md.subcode
WHERE de.ShortenCode = t1.ShortenCode
) t2
如果您有任何建议,我将不胜感激
最佳答案
我想你可以尝试像这样在 SELECT 部分获取子查询
SELECT DISTINCT( de.MCH_CODE) AS Mach, md.MAT_CODE as ShortenCode, de.TIME as
start_time,
(SELECT dee.MCH_CODE FROM table1 AS dee JOIN table1table2 AS mdd
ON dee.subcode= mdd.subcodewhere md.MAT_CODE = mdd.MAT_CODE and
dee.MCH_CODE < de.MCH_CODE order by dee.MCH_CODE DESC LIMIT 1) as prevMach
FROM table1 AS de
JOIN table1table2 AS md
ON de.subcode= md.subcode
WHERE de.ev = '123' AND de.time > '2017-11-14 07:00' and de.side = 'R'
AND de.end IS NULL AND de.Subcat = 'STOP'
ORDER BY de.time
尽管我猜测根据索引和数据量计算可能需要很长时间。
关于mysql - SQL 中的嵌套查询,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/47328691/