SQL Server 2008 R2:从列中获取第一个非空值
我有以下表格来显示预期结果 表格:SQL Server 2008 R2:从列中获取第一个非空值,sql,sql-server,sql-server-2008-r2,Sql,Sql Server,Sql Server 2008 R2,我有以下表格来显示预期结果 表格: CREATE TABLE Family ( ID int, Name varchar(20), Gender char(1) ); INSERT INTO Family VALUES (1,'Ram','M'), (2,'Suraj','M'), (3,'Sunitha','F'), (4,'Deepika','F'), (5,'Minakshi','F'), (6,'Somu','M'); CREATE TABLE Child_p
CREATE TABLE Family
(
ID int,
Name varchar(20),
Gender char(1)
);
INSERT INTO Family VALUES
(1,'Ram','M'),
(2,'Suraj','M'),
(3,'Sunitha','F'),
(4,'Deepika','F'),
(5,'Minakshi','F'),
(6,'Somu','M');
CREATE TABLE Child_parent
(
Child_ID int,
Parent_ID int
);
INSERT INTO Child_parent VALUES
(1,2),
(1,3),
(4,5),
(4,6);
预期结果:
Child_ID ChildName FatherName MotherName
-----------------------------------------------
1 Ram Suraj Sunitha
4 Deepika Somu Minakshi
SELECT cp.Child_ID,
f1.Name as ChildName,
CASE WHEN f2.Gender = 'M' THEN f2.Name END FatherName,
CASE WHEN f2.Gender = 'F' THEN f2.Name END MotherName
FROM Child_parent cp
LEFT JOIN Family f1
ON cp.Child_ID = f1.ID
LEFT JOIN Family f2
ON cp.Parent_ID = f2.ID
我的尝试:
Child_ID ChildName FatherName MotherName
-----------------------------------------------
1 Ram Suraj Sunitha
4 Deepika Somu Minakshi
SELECT cp.Child_ID,
f1.Name as ChildName,
CASE WHEN f2.Gender = 'M' THEN f2.Name END FatherName,
CASE WHEN f2.Gender = 'F' THEN f2.Name END MotherName
FROM Child_parent cp
LEFT JOIN Family f1
ON cp.Child_ID = f1.ID
LEFT JOIN Family f2
ON cp.Parent_ID = f2.ID
但得到的结果表明:
Child_ID ChildName FatherName MotherName
----------------------------------------------
1 Ram Suraj NULL
1 Ram NULL Sunitha
4 Deepika NULL Minakshi
4 Deepika Somu NULL
试试这个
SELECT cp.Child_ID,
f1.Name as ChildName,
max(CASE WHEN f2.Gender = 'M' THEN f2.Name END) FatherName,
max(CASE WHEN f2.Gender = 'F' THEN f2.Name END) MotherName
FROM Child_parent cp
LEFT JOIN Family f1
ON cp.Child_ID = f1.ID
LEFT JOIN Family f2
ON cp.Parent_ID = f2.ID
group by cp.Child_ID,
f1.Name
order by cp.Child_ID
这是一个具有单个
连接的替代解决方案
SELECT CP.Child_ID,
MAX(CASE WHEN CP.Parent_ID <> F.ID THEN F.Name END) ChildName,
MAX(CASE WHEN CP.Parent_ID = F.ID AND F.Gender ='M' THEN F.Name END) FatherName,
MAX(CASE WHEN CP.Parent_ID = F.ID AND F.Gender ='F' THEN F.Name END) MotherName
FROM
Child_parent CP
LEFT JOIN Family F ON CP.Parent_ID = F.ID OR CP.Child_ID = F.ID
GROUP BY
Child_ID
选择CP.Child\u ID,
MAX(CP.Parent\u ID F.ID然后F.Name END时的情况)ChildName,
MAX(当CP.Parent\u ID=F.ID,F.Gender='M'然后F.Name END时的情况)FatherName,
MAX(CP.Parent_ID=F.ID,F.Gender='F'然后F.Name END时的情况)MotherName
从…起
子/父CP
在CP.Parent\u ID=F.ID或CP.Child\u ID=F.ID上左连接族F
分组
儿童身份证