php - 如何在一个sql查询中多次使用where条件

Question

在我的table1中有这样的日期:

id      value
1       500
2       400
3       300
4       200
5       100

我想在显示表中设置上面的数据:

d1      d2      d3      d4      d5
500     400     300     200     100

我正在使用以下 SQL 查询。

"SELECT `value` as d1 from `table1` WHERE `id`=1"
"SELECT `value` as d2 from `table1` WHERE `id`=2"
"SELECT `value` as d3 from `table1` WHERE `id`=3"
"SELECT `value` as d4 from `table1` WHERE `id`=4"
"SELECT `value` as d5 from `table1` WHERE `id`=5"   

如何在单个 SQL 查询中进行所有查询？

Answer 1

我会使用聚合:

select max(case when id = 1 then value end) as d1,
       max(case when id = 2 then value end) as d2,
       max(case when id = 3 then value end) as d3,
       max(case when id = 4 then value end) as d4,
       max(case when id = 5 then value end) as d5
from t;