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您好，我有带有数据和 2 个小问题的表格结构。

CREATE TABLE [dbo].[Parent] (
    [id] [int] NOT NULL,
    [Name] [nvarchar](50) NOT NULL, 
 CONSTRAINT [PK_Parent] PRIMARY KEY CLUSTERED 
(
    [id] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

CREATE TABLE [dbo].[Child1] (
    [Child1Id] [int] NOT NULL,
    [ParentId] [int] NOT NULL,
    [SomeData] [int] NOT NULL,  
 CONSTRAINT [PK_Child1] PRIMARY KEY CLUSTERED 
(
    [Child1Id] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

CREATE TABLE [dbo].[Child2] (
    [Child2Id] [int] NOT NULL,
    [ParentId] [int] NOT NULL,
    [SomeData] [int] NOT NULL,  
 CONSTRAINT [PK_Child2] PRIMARY KEY CLUSTERED 
(
    [Child2Id] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]


INSERT INTO Parent VALUES(1,'Name 1')
INSERT INTO Parent VALUES(2,'Name 2')
INSERT INTO Parent VALUES(3,'Name 3')
INSERT INTO Parent VALUES(4,'Name 4')


INSERT INTO [Child1] VALUES(1,1,50)
INSERT INTO [Child1] VALUES(2,1,125)
INSERT INTO [Child1] VALUES(3,2,255)


INSERT INTO [Child2] VALUES(1,1,2)
INSERT INTO [Child2] VALUES(2,2,4)
INSERT INTO [Child2] VALUES(3,2,8)
INSERT INTO [Child2] VALUES(4,3,16)

  1. 如何选择两个表中至少具有一种子类型的所有 parets 记录。我做了下一个查询，但我不知道显示此记录总数的最佳方法

    SELECT p.Name, count(Child1) , count(Child2)

  2. 如何选择仅存在于两个表中的所有 parets 记录？SELECT p.Name, count(Child1) , count(Child2)

感谢您的建议。

4

1 回答 1

2

查询一：

--at least one child record in either Child1 or Child2
select distinct p.*
from parent p
left outer join child1 c1 on p.id = c1.ParentId
left outer join child2 c2 on p.id = c2.ParentId
where coalesce(c1.ParentId, c2.ParentId) is not null

查询 2：

--at least one child record in both Child1 and Child2
select distinct p.*
from parent p
inner join child1 c1 on p.id = c1.ParentId
inner join child2 c2 on p.id = c2.ParentId

注意：如果您只想显示父记录的计数，请更改

select distinct p.*

到

select count(distinct p.id)

在任一查询中。

于 2012-05-10T15:52:50.833 回答