Mysql数据库高级SQL

1、从一个表更新到另外一个表

方法一

UPDATE temp_x a, temp_y b SET a.`c_amount` = b.`c_amount` WHERE a.`c_id` = b.`c_id`;

方法二、

UPDATE temp_x a SET a.`c_amount` = (SELECT b.c_amount FROM temp_y b WHERE b.`c_id` = a.`c_id`)

2、多字段排序

if test="dto.mindSort!=null and dto.mindSort=='4'.toString()">

dict.sort ASC,reportStatus desc,

case reportDay

when '申请中' then '1'

when '长期可申报' then '2'

when '无需申报' then '3'

when '申报结束' then '4'

end asc

if>

3、获取当前时间的月份

select MONTH(DATE_SUB(CURDATE(),INTERVAL 1 MONTH)) from dual;

获取当前月份的上个月月份

DATE_SUB(CURDATE(),INTERVAL 1 MONTH)

4、表中有重复数据，如果去重查询数据

select a.* from taxation_data a join (select social_credit_code,max(base_id) best_history_data from taxation_data group by social_credit_code) b where a.social_credit_code=b.social_credit_code and a.base_id=b.best_history_data;