mysql取差集.交集.并集 博客分类: Mysql数据库 需求:从两个不同的结果集(一个是子集,一个是父集),字段为电话号码phone_number,找出父集中缺少的电话号码,以明确用户身份. 结合网上资料,整理sql如下: //mysql取差集 Java代码 收藏代码 select num FROM ( select u.code_sn as id,u.phone_number as num from t1 b left join t2 u on b.from_user=u.code_sn
方法:mysql取分组后最新的一条记录,下面两种方法.一种是先筛选 出最大和最新的时间,在连表查询.一种是先排序,然后在次分组查询(默认第一条),就是最新的一条数据了 #select * from t_assistant_article as a, (select max(base_id) as base_id, max(create_time) as create_time from t_assistant_article as b group by base_id ) as b where
一.JSON类型 答案是不可以 为Json类型建索引会报错 mysql)); ERROR (): JSON column 'card_pay_data' cannot be used in key specification. 二.text类型 答案是可以的,但是需要指定长度 mysql> CREATE INDEX idx2 ON user (tests); ERROR (): BLOB/TEXT column 'tests' used in key specification without
SELECT name, profile->"$.twitter" AS `twitter` FROM `user` WHERE profile->"$.twitter" IS NOT NULL; https://dev.mysql.com/doc/refman/5.7/en/json-search-functions.html https://www.sitepoint.com/use-json-data-fields-mysql-databases/
MySQL 5.7.8开始支持 json类型. create table t(id int,js json,PRIMARY KEY (`id`)) 插入数据insert into t values(1,'{"a":1,"s":"abc"}')insert into t values(2,'[1,2,{"a":123}]')insert into t values(3,'"str"')insert into