sql - 将行查询到列中

Question

我在 tbl1 中有数据:

item    date    amount
a   1   10
a   2   20
a   3   30
a   4   40
b   1   20
b   2   30
b   3   40
b   4   50
c   1   30
c   2   40
c   3   50
c   4   60

但我需要像下面这样

item    1   2   3   4
a   10  20  30  40
b   20  30  40  50
c   30  40  50  60

Answer 1

使用PIVOT

SELECT item, [1], [2], [3], [4]
FROM tbl1 t
PIVOT (SUM(amount) FOR date IN ([1], [2], [3], [4])) p
SELECT item, [10], [20], [30], [40], [50], [60]
FROM tbl1 t
PIVOT (MAX(date) FOR amount IN ([10], [20], [30], [40], [50], [60])) p

输出:

item    1   2   3   4
a       10  20  30  40
b       20  30  40  50
c       30  40  50  60

SQL fiddle :http://sqlfiddle.com/#!3/f097d/12/0