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MYSQL 按字段 A 查询,此表中字段 A 重复的话,字...

select 字段A,sum(字段B) from 表A group by 字段A order by 字段A你试试这个

如果每一行的id与bill_id不相同的话,可以 update tset bill_details_idx = ( select count(t1.r) from (select id,bill_id,1 r from t) t1 where t.bill_id=t1.bill_id and t1.id

select articleid,count(*) as zongshu from table where typeid in ('评论','留言') group by articleid order by zongshu desc;

select t1.a , (select top 1 t2.b from table2 as t2 where t2.b = t1.a and 额外条件1) as 对应于额外条件的列名1, (select top 1 t2.b from table2 as t2 where t2.b = t1.a and 额外条件2) as 对应于额外条件的列名2, (select top 1 t2.b fr...

SELECT * FROM names;+----+--------+| id | name |+----+--------+| 1 | google || 2 | yahoo || 3 | msn || 4 | google || 5 | google || 6 | yahoo | 想保留最大id的话: DELETE FROM NAMES WHERE id NOT IN (SELECT * FROM (SELECT MAX(n.id...

select a.id,count(*) from a,b where a.id=b.aid group by a.id

试试这个方法:SELECT id, name, (SELECT comment_id, title, content FROM B WHERE user_id = A.id ORDER BY create_time DESC LIMIT 1) FROM A;

如果 abc重复 d 不重复怎么取数?

create table B LIKE A 这种方法建立,会不带任何数据,但是会带着表A的主键,约束等 create table B select * from A 这种方法建立,会带着数据,但是不会带着表A的主键,约束等

select * from a,b,c where a.id=b.id and b.id=c.id and max(b.ziduan); 你得保证这3张表能连起来

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