查找表中作为列两个领域之间的区别

Question

我有以下

SELECT 
ttstudent.ttstudentid, 
ttstudent.studentid, 
ttstudent.subjectid, 
ttstudent.classnumber, 
ttstudent.classid, 
concat(student.fn, " ", student.sn) AS Student, 
SUM(If(ondemand.cycle="Feb7" and ondemand.type="Numeracy", ondemand.Score, NULL)) AS `Yr7 Feb`, 
SUM(If(ondemand.cycle="Jul7" and ondemand.type="Numeracy", ondemand.Score, NULL)) AS `Yr7 July`, 
SUM(If(ondemand.cycle="Feb8" and ondemand.type="Numeracy", ondemand.Score, NULL)) AS `Yr8 Feb`, 
SUM(If(ondemand.cycle="Jul8" and ondemand.type="Numeracy", ondemand.Score, NULL)) AS `Yr8 July`, 
SUM(If(ondemand.cycle="Feb9" and ondemand.type="Numeracy", ondemand.Score, NULL)) AS `Yr9 Feb`, 
SUM(If(ondemand.cycle="Jul9" and ondemand.type="Numeracy", ondemand.Score, NULL)) AS `Yr9 July`, 
SUM(If(ondemand.cycle="Feb10" and ondemand.type="Numeracy", ondemand.Score, NULL)) AS `Yr10 Feb`, 
SUM(If(ondemand.cycle="Jul10" and ondemand.type="Numeracy", ondemand.Score, NULL)) AS `Yr10 Aug`, 
ondemand.Student_ID 
FROM ttstudent 
INNER JOIN student ON ttstudent.studentid = student.code 
INNER JOIN ondemand ON ttstudent.studentid = ondemand.Student_ID 
GROUP BY ondemand.Student_ID 

这产生了25人左右的柱状清单与最后一列找到最后2之差计算字段下面的SQL表中的值。得分是时间戳。

CODE |Year7Feb|Year7Jul|Year8Feb|Year8Jul|Year9Feb|Year9Jul| Year10Feb| Growth 
abe1 | 2.3 | 2.9 |  |  |  |  |   | .6 
bas1 |  |  | 3.5 | 3.7 |  |  |   | .2 
cod |  |  |  |  |  | 4.5 | 5.2 | .7 

我想这样做是另一列添加这将需要从每个用户（无论列它是）最后两个得分并找到差异。我会称这一列增长。

我正在努力使用以外的最大值。有任何想法吗？

Answer 1

这应该做的伎俩：

计算列growth用下面的查询

SELECT si,ty,la.uid laid,pr.uid prid,(la.score-pr.score) growth FROM ( 
SELECT si,ty,max(test_date) cyprev, cylast FROM ondemand INNER JOIN (
    SELECT Student_ID si,type ty,max(test_date) cylast FROM ondemand 
     GROUP BY Student_ID,type 
) od ON si=Student_ID AND ty=type AND cylast>test_date 
GROUP BY si,ty, cylast 
) getlast2 
INNER JOIN ondemand la ON la.Student_Id=si AND la.type=ty AND la.test_date=cylast 
INNER JOIN ondemand pr ON pr.Student_Id=si AND pr.type=ty AND pr.test_date=cyprev 

，然后LEFT JOIN到您的整个查询（略简化此版本）：

SET @subj:="Numeracy"; 
SELECT Student_id, 
SUM(If(ondemand.cycle="Feb7" and ondemand.type=@subj, ondemand.Score, NULL)) AS `Yr7 Feb`, 
SUM(If(ondemand.cycle="Jul7" and ondemand.type=@subj, ondemand.Score, NULL)) AS `Yr7 July`, 
SUM(If(ondemand.cycle="Feb8" and ondemand.type=@subj, ondemand.Score, NULL)) AS `Yr8 Feb`, 
SUM(If(ondemand.cycle="Jul8" and ondemand.type=@subj, ondemand.Score, NULL)) AS `Yr8 July`, 
SUM(If(ondemand.cycle="Feb9" and ondemand.type=@subj, ondemand.Score, NULL)) AS `Yr9 Feb`, 
SUM(If(ondemand.cycle="Jul9" and ondemand.type=@subj, ondemand.Score, NULL)) AS `Yr9 July`, 
SUM(If(ondemand.cycle="Feb10" and ondemand.type=@subj, ondemand.Score, NULL)) AS `Yr10 Feb`, 
SUM(If(ondemand.cycle="Jul10" and ondemand.type=@subj, ondemand.Score, NULL)) AS `Yr10 Aug`, 
growth 
FROM ondemand LEFT JOIN (
SELECT si,ty,la.uid laid,pr.uid prid,(la.score-pr.score) growth FROM ( 
    SELECT si,ty,max(test_date) cyprev, cylast FROM ondemand INNER JOIN (
    SELECT Student_ID si,type ty,max(test_date) cylast FROM ondemand 
      GROUP BY Student_ID,type 
) od ON si=Student_ID AND ty=type AND cylast>test_date 
    GROUP BY si,ty, cylast 
) getlast2 
INNER JOIN ondemand la ON la.Student_Id=si AND la.type=ty AND la.test_date=cylast 
INNER JOIN ondemand pr ON pr.Student_Id=si AND pr.type=ty AND pr.test_date=cyprev 
) gt ON si=Student_id AND ty=@subj 
GROUP BY Student_id; 

我忽略了JOIN s到表student和ttstudent及其列

ttstudent.ttstudentid, 
ttstudent.studentid, 
ttstudent.subjectid, 
ttstudent.classnumber, 
ttstudent.classid, 
concat(student.fn, " ", student.sn) AS Student 

编辑：

刚才用你test_date列的变化。子查询在MySQL中进行了测试，我希望它也可以在您的数据库中使用。

EDIT2：

我慢慢看到你从哪里来。它变得越来越复杂（刚填充有关type="Numeracy"的XTRA条件......也许还有毕竟是一个简单的解决方案？

不管怎么说，这是一个SQLfiddle证明整个事情（在这里修改后的版本：sqlfiddle2）

第三次和最后编辑：

你可能需要的是对SQLfiddle3东西线（ - >只一个 SELECT命令没有前面的SET声明）。你完整的命令应该再是这个样子：

SELECT 
ttstudent.ttstudentid, 
ttstudent.studentid, 
ttstudent.subjectid, 
ttstudent.classnumber, 
ttstudent.classid, 
concat(student.fn, " ", student.sn) AS Student, 
SUM(If(ondemand.cycle="Feb7" and ondemand.type="Numeracy", ondemand.Score, NULL)) AS `Yr7 Feb`, 
SUM(If(ondemand.cycle="Jul7" and ondemand.type="Numeracy", ondemand.Score, NULL)) AS `Yr7 July`, 
SUM(If(ondemand.cycle="Feb8" and ondemand.type="Numeracy", ondemand.Score, NULL)) AS `Yr8 Feb`, 
SUM(If(ondemand.cycle="Jul8" and ondemand.type="Numeracy", ondemand.Score, NULL)) AS `Yr8 July`, 
SUM(If(ondemand.cycle="Feb9" and ondemand.type="Numeracy", ondemand.Score, NULL)) AS `Yr9 Feb`, 
SUM(If(ondemand.cycle="Jul9" and ondemand.type="Numeracy", ondemand.Score, NULL)) AS `Yr9 July`, 
SUM(If(ondemand.cycle="Feb10" and ondemand.type="Numeracy", ondemand.Score, NULL)) AS `Yr10 Feb`, 
SUM(If(ondemand.cycle="Jul10" and ondemand.type="Numeracy", ondemand.Score, NULL)) AS `Yr10 Aug`, 
ondemand.Student_ID, 
getdif.growth 
FROM ttstudent 
INNER JOIN student ON ttstudent.studentid = student.code 
INNER JOIN ondemand ON ttstudent.studentid = ondemand.Student_ID 
LEFT JOIN (
SELECT si,ty,la.uid laid,pr.uid prid,(la.score-pr.score) growth FROM ( 
    SELECT si,ty,max(test_date) cyprev, cylast FROM ondemand INNER JOIN (
    SELECT Student_ID si,type ty,max(test_date) cylast FROM ondemand 
      GROUP BY Student_ID,type 
) od ON si=Student_ID AND ty=type AND cylast>test_date 
    GROUP BY si,ty, cylast 
) getlast2 
INNER JOIN ondemand la ON la.Student_ID=si AND la.type=ty AND la.test_date=cylast 
INNER JOIN ondemand pr ON pr.Student_ID=si AND pr.type=ty AND pr.test_date=cyprev 
) getdif ON si=ondemand.Student_ID AND ty=ondemand.type 
WHERE ondemand.type='Numeracy' 
GROUP BY ondemand.Student_ID 

我以前的版本中体现我的个人避免任何冗余的偏爱，也是我的志向参数化的东西尽可能。但是我可能走得太远了;-)。