mysql - 根据 MySQL 中的值选择字段

Question

有mysql表foo：

a | b | c
----------
1 | 2 | 0
2 | 3 | 1
3 | 4 | 0

和一个查询

SELECT a-b as subA, b-a as subB FROM foo;

subA | subB
-----------
 -1  |   1
 -1  |   1
 -1  |   1

我如何选择a-b as sum如果 c = 0 和b-a as sum如果 c = 1，以便我得到这个结果：

sum
---
-1
 1
-1

标签： mysqlsqlcase

Answer 1

SELECT (a-b)*(1-2*c) AS `sum`
FROM foo