CASE WHEN用法

 1 SELECT
 2     `s`.*, (
 3         CASE
 4         WHEN `a`.`status` > 1 THEN
 5             SUM(a.total_number)
 6         WHEN `a`.`status` <= 1 THEN
 7             NULL
 8         END
 9     ) AS sales
10 FROM
11     `ce_order` `a`
12 INNER JOIN (
13     SELECT
14         `s`.*, b.company_name AS bloc_name
15     FROM
16         `ce_store` `s`
17     INNER JOIN `ce_bloc` `b` ON `s`.`bid` = `b`.`id`
18 ) s ON `a`.`uid` = `s`.`id`
19 GROUP BY
20     s.id