论坛表的MS Access sql查询

如果你会发现这个问题对于论坛来说很简单 - 将责任归咎于我，我会道歉，因为我不过是这个问题的新手。论坛表的MS Access sql查询

我在MS访问这两个表：

表项和表评论由Comments.parent ID = Items.ID连接。

我需要将显示最近10条记录，从项目表的查询，包含

Item.id 
Item.title 
Item.text 
Item,date_modified 
count of Comments [if any] for the Item 
last Comments[if any] guestName 
last Comments[if any] date_modified

到目前为止，我有这样的事情每个记录：

 
SELECT TOP 10 t4.id, t4.* FROM 
(
SELECT Items.id AS item_id , Items.*, t3.guestName , t3.modified AS comment_date 
,(SELECT count(*) FROM Comments where parentid = Items.id) as comentscount 
FROM Items 
,(SELECT t2.id as commentID, t2.guestName , t2.modified, t2.parentid FROM Comments as t2 ORDER BY t2.modified DESC ) as t3 
WHERE 
(Items.id = t2.parentid AND t3.commentID = (SELECT max(id) FROM Comments where parentid = Items.id)) 
ORDER BY Items.modified DESC 

UNION 

SELECT Items.id AS item_id, Items.* , null AS guestName, null AS comment_date, 
(SELECT count(*) FROM Comments where parentid = Items.id) as comentscount 
FROM Items 
WHERE (SELECT count(*) FROM Comments where parentid = Items.id) = 0 
) AS t4

嘛。它正在工作，但我一直在问自己，如果这可以以更简单的方式完成。

任何建议将更受欢迎。

预先感谢您。

来源

2010-11-21 novice17

Flinsch和Remou，非常感谢你对你的反应。我必须做一些小的调整，但你发送的一般想法对我来说都非常有用。这两个例子都让我朝着正确的方向前进，以提高自己的SQL知识，并使查询顺利进行。 – novice17 2010-11-22 11:38:57

SELECT TOP 10 
Item.id, 
Item.title, 
Item.text, 
Item.modified, 
COUNT(Comment.id) AS count_of_comments, 
(SELECT TOP 1 Comment.guest_name FROM Comment WHERE Comment.parentid = Item.id ORDER BY Comment.modified DESC) AS last_guest_name, 
MAX(Comment.modified) AS last_comment_date 
FROM Item 
LEFT JOIN Comment ON Comment.parentid = Item.id 
GROUP BY Item.id 
ORDER BY Item.modified DESC

我不确定内部SELECT声明是否也可以更适当地集成。也许我们也可以ORDER BY Comments.modified DESC，然后只是“选择”guest_name拒绝嵌套的SELECT声明，但我不确定。

（我没有测试过。）

来源

2010-11-21 19:08:40 Flinsch

谢谢Flinsch。我有你的例子是这样工作的： SELECT TOP 10 Items.id，Items.title，Items.text，Items.modified， COUNT（Comments.id）AS count_of_comments，（SELECT TOP 1 Comments.guest_name FROM Comments WHERE Comments.parentid = Items.id ORDER BY Comment.modified DESC）AS last_guest_name，（SELECT TOP 1 Comments.modified FROM Comments WHERE Comments.parentid = Items.id ORDER BY Comments.modified DESC） AS last_comment_date FROM Items LEFT JOIN Comments on Comments.parentid = Items.id GROUP BY Items.id ORDER BY Items.modified DESC – novice17 2010-11-22 11:42:22

如何上线的东西：

SELECT TOP 10 
     Item.id, 
     Item.title, 
     Item.text, 
     Item.date_modified, 
     c.CommentCount, 
     c.LastComment, 
     c.LastGuestName, 
     c.LastModDate 
FROM Item 
LEFT JOIN 
(SELECT ParentID, 
     Count(ParentID) As CommentCount, 
     Last(Comment) As LastComment, 
     Last(guestName) As LastGuestName, 
     Last(date_modified) As LastModDate 
FROM Comments 
GROUP BY ParentID 
ORDER BY date_modified DESC) c 
ON Item.ItemID=c.ParentID 
ORDER BY item.date_modified

来源

2010-11-21 19:18:32 Fionnuala

谢谢Remou。我有你的例子如下工作： SELECT TOP 10 Items.id， Items.titel， Items.text， Items.modified ，c.commentsCOUNT ，c.guest ，C。commentDATE 从装备 LEFT JOIN （SELECT parentId的，计数（parentId的）AS commentsCOUNT，LAST（guest虚拟机名称）作为嘉宾，LAST（修改）AS commentDATE，LAST（文本）自评 GROUP BY PARENTID ORDER BY LAST（修改）DESC）c ON Items.Id = c.ParentId ORDER BY items.modified DESC – novice17 2010-11-22 11:43:37

论坛表的MS Access sql查询

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