MySQL中if的写法

关键词：IF

--if 判断，如果 device_num 的值为1，则赋值为100，反之为200
SELECT
    district,
    shop_name,
IF
    ( device_num = 1, 100, 200 ) AS device_num 
FROM
    `t_life_shop`

 关键词：CASE

-- CASE WHEN（新增一个字段type值为，如果group_id = 1则type=1,如果group_id = 10则type=3,反之type=2）
SELECT
    uid,
    user_name,
    group_id,
    (
        CASE
        WHEN group_id = 1 THEN
            1
        WHEN group_id = 10 THEN
            3
        ELSE
            2
        END
    ) AS type
FROM
    t_sys_user;