mysql - MySQL：如何查询多个表并仅对一个表应用 LIMIT？

Question

假设我有一个包含items的表和另一个包含subitems的表。我想返回与有限数量的项目相关的所有子项目。本质上，我想加入这两个查询：

SELECT * FROM subitem

SELECT * FROM item LIMIT 10

其中subitem.item = item.id：

我试过这个：

SELECT * FROM subitem INNER JOIN item ON subitem.item = item.id LIMIT 10

但是，此查询仅返回 10 个子项（如您所料）。我想检索所有子项，同时仅将项目数限制为 10。我该如何实现？

Answer 1

这将为您提供 10 件物品。但是，您应该添加 WHERE 子句和 ORDER BY 子句来获取您要查找的项目。

SELECT * FROM subitem INNER JOIN 
              (SELECT * FROM items LIMIT 10) AS I
              ON subitem.item = I.id 

Answer 2

尝试以下查询：

select * from item,subitem where id = item and 
  id in (select id from item limit 10)

IN如果in有问题LIMIT，请尝试以下查询：

select * from (select id from item limit 10) as i1, subitem where id =item ;

Answer 3

也许是这样的：

SELECT * FROM subitem WHERE item IN (SELECT id FROM item LIMIT 10);

Answer 4

如何在此查询中使用限制

select tbl_thread.id,user_id,name,tbl_User.alert_flag,thread_name,thread_status,(select CAST(count(*) as UNSIGNED) from tbl_message where thread_id=tbl_thread.id AND read_status='0' and msg_from='EU' ) as unread,thread_timestamp,(select CAST(max(id) as UNSIGNED) from tbl_message where thread_id=tbl_thread.id) as max_id from tbl_thread,tbl_User where tbl_User.UserID=user_id ;