特殊sql查询方法实例

一、if条件查询：
SELECT
sum(if(is_buy > 0 ,1,0)) AS friend_count_all_cj,
sum(if(is_buy = 0 ,1,0)) AS friend_count_all_wcj
FROM
anis_chat_order
WHERE
uid = '521'
AND wx_id = '356'

二、case when 查询：
SELECT
sum(CASE WHEN is_buy > 0 THEN 1 else 0 END) AS friend_count_all_cj,
sum(CASE WHEN is_buy = 0 THEN 1 else 0 END) AS friend_count_all_wcj
FROM
anis_chat_order
WHERE
uid = '521'
AND wx_id = '356'

三、查询指定日期局今天的天数
select DATEDIFF(NOW(),要查询的字段) as day_count from 表