Mysql垂直组合2列（不要求concat）

Question

我有一张包含2个cols的表：

category count
x0         10
x1         20
x2         30
x3         40

我想将category x1和x3合并为x1，将相应的count值合并为(20 +40 =60) < / p>

所需的结果如下：

category count
x0         10
x1         60
x2         30

Answer 1

UPDATE `table` 
SET `count` = ( SELECT * 
                FROM ( SELECT SUM(`count`) 
                       FROM `table` 
                       WHERE `category` IN ('x1','x3') 
                     ) x
              ) 
WHERE `category` = 'x1';

DELETE FROM `table` 
WHERE `category` = 'x3';

SQLFiddle

Answer 2

SELECT IF(category = 'x3', 'x1', category) AS adjusted_category
     , SUM(count) AS `count` 
FROM ... 
GROUP BY adjusted_category

编辑：已修复。