sql - 不同列上的 SQL 子字符串

Question

我有一个带有列的数据库表METADATA。这METADATA可能包含也可能不包含字符串。这是示例字符串：

StudentID:1234,StudentName:TestName,StudentNickName:TestNName,StudentLevel:5

现在，我想提取 StudentNickName:TestName（如果存在）。请注意以下约束：

• METADATA列并不总是包含值
• METADATA列可以包含一个没有StudentNickName子句的值
• StudentNickName:是固定的，而每TestNName行不同。

Answer 1

对于 mssql 2005+

declare @t table(metadata varchar(200))
insert @t values('StudentID:1234,StudentName:TestName,StudentNickName:TestNName,StudentLevel:5')
insert @t values('')
insert @t values('StudentID:1234,StudentName:Thomas,StudentNickName:Tom,StudentLevel:3')


select left(b.a, patindex('%_,%', b.a)) StudentNickName
from @t t cross apply
(select right(metadata, patindex('%_:emaNkciNtnedutS%'
 , reverse('X'+ metadata)))+',' a) b

结果：

StudentNickName
---------------
TestNName

Tom

Answer 2

在 Sql Server 中工作

DECLARE @test TABLE(metadata VARCHAR(200))
INSERT @test VALUES('StudentID:1234,StudentName:TestName,StudentNickName:TestNName,StudentLevel:5')
INSERT @test VALUES('StudentID:1235,StudentName:TestName1,StudentNickName:TestNName1,StudentLevel:6')
INSERT @test VALUES('StudentID:1236,StudentName:TestName2,StudentNickName:TestNName2,StudentLevel:2')
INSERT @test VALUES('')

SELECT split.s.value('.','VARCHAR(100)') as colname FROM 
(
    SELECT CAST('<s>' + REPLACE(metadata,',','</s><s>') + '</s>' AS XML) col FROM @test
) AS t CROSS APPLY col.nodes('/s') AS split(s)
WHERE split.s.value('.','VARCHAR(100)') LIKE '%StudentNickName%'