修改c字段=a字段+b字段用，拼接

update tab set c=IFNULL(concat(a,',',b),a);

修改字段+1或者-1

update tab set praise_num = praise_num + 1 where id = #{id,jdbcType=INTEGER}

update tab set praise_num = praise_num - 1  where id = #{id,jdbcType=INTEGER}

模糊查询

like CONCAT(#{word,jdbcType=VARCHAR},'%')

like CONCAT('%>',CONCAT(#{deptId},'>%' )）

根据当前时间判断一个活动的状态：1已结束，2进行中，3未开始

CASE WHEN end_time < #{nowTime,jdbcType=TIMESTAMP} THEN 1

WHEN start_time <= #{nowTime,jdbcType=TIMESTAMP} 

AND end_time >= #{nowTime,jdbcType=TIMESTAMP} THEN 2

WHEN.start_time >= #{nowTime,jdbcType=TIMESTAMP} THEN 3

END as status,

一对多的查询，字段用逗号拼接展示

GROUP_CONCAT(t2.tag) AS activityTag

GROUP BY t1.id

时间

date_format(a.begin_date, '%Y-%m-%d')

WHERE date(click_date) = curdate()