Mysql 垂直合并 2 列(不要求连接)

Question

我有一个包含 2 列的表格:

category count
x0         10
x1         20
x2         30
x3         40

我想把categoryx1和x3组合起来命名为x1和对应的count 值是总和 (20 +40 =60)

期望的结果如下:

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