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mysql 集合

我的想法是:用Union all 你试一下,我没数据,没办法测试: select id, sum(num) from ((select id, sum(num) num from tables1 group by id) union all (select id, sum(num) num from tables2 group by id)) a group by id

思路为: 需要把集合中的每个元素分别取出 取出以后写SQL语句 把每个元素写入到insert语句中进行向数据库的插入 说明:代码中要实现连接数据库及相关业务逻辑,要根据实际情况来写 List list = new ArrayList();list.add("a");list.add("b");for...

集合(SET) mysql> create table jihe(f1 set('f','m')); Query OK, 0 rows affected (0.11 sec) mysql> desc jihe; +-------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+----...

CREATE TABLE A (id int);CREATE TABLE B (id int);INSERT INTO A VALUES(1);INSERT INTO A VALUES(2);INSERT INTO A VALUES(3);INSERT INTO B VALUES(1);INSERT INTO B VALUES(2);INSERT INTO B VALUES(3);INSERT INTO B VALUES(4);INSERT INTO...

select * from ((SELECT uid,je,starttime,stoptime,1 as type from (SELECT id from members WHERE referer='4') as m JOIN (SELECT uid,je,starttime,stoptime from `cz` WHERE `status`>0) as c on c.uid=m.id)union(SELECT uid,je,starttime...

把数组变成字符串:比如$a=array{"12","23","34","45"}; $a="12,23,34,45"; 把这个存到数据库中就行了 读取时再用explode变成数组

DELIMITER //CREATE DEFINER=`root`@`%` PROCEDURE testProc()BEGIN SELECT 'Hello 1' AS A, 'World 1' AS B UNION ALL SELECT 'Hello 2' AS A, 'World 2' AS B;END //DELIMITER ;mysql> call testProc();+---------+---------+| A | B |+------...

flag字段定义的集合里的字符串的任意集合 如定义flag('a,b,c,d'); 则值可以为 'a' or 'a,c',or 'a,b,c'等等

查询 表的id 条件是姓名字段等于要查的姓名,返回的就是id

MySQL中的UNION ALL 而UNION ALL只是简单的将两个结果合并后就返回。这样,如果返回的两个结果集中有重复的数据,那么返回的结果集就会包含重复的数据了。 从效率上说,UNION ALL 要比UNION快很多,所以,如果可以确认合并的两个结果集中不包含...

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