SQL Server中的逗号分隔操作

Question

Table 1 :

T1Id      Name    SchoolIds
------------------------------
01        A       1,2,3,4
02        B       4,20,3,1
03        C       20,30,40
04        D       30,20,10,2

Table 2 :

T2ID        SchoolIds       Username
--------------------------------------
01          1,2,3,4         a@a.com
02          20,30,40,2      b@a.com
03          30,20,10,2      c@a.com
04          4,20,3,1        d@a.com

There are two pages, one is login and other is records.

When someone is logging in with username='a@a.com' and then goes for records, then the code should display only those rows from Table1 which are a match with columns SchoolIds from Table 1.

if login with a@a.com the desired result would be:

T1Id      Name     SchoolIds
-----------------------------
01        A        1,2,3,4
02        B        4,20,3,1
04        D        30,20,10,2

Answer 1

First of all, do not store items as comma separated string.

Instead, go for a new table with foreign keys attached to the parent table. That will also allow you to easily get the required data.

So my advice is to create new table and store each item as separate rows with some matching id to parent table :)

Answer 2

It seems Big, But it gives what you want. Is any suggestions, kindly put in the comments.

DECLARE @Table1 TABLE(T1ID INT, Name VARCHAR(1), SchoolIds VARCHAR(20))
INSERT INTO @Table1 VALUES(01,'A','1,2,3,4')
INSERT INTO @Table1 VALUES(02,'B','4,20,3,1')
INSERT INTO @Table1 VALUES(03,'C','20,30,40')
INSERT INTO @Table1 VALUES(04,'D','30,20,10,2')

DECLARE @Table2 TABLE(T2ID INT, SchoolIds VARCHAR(20), Username VARCHAR(20))
INSERT INTO @Table2 VALUES(01,'1,2,3,4','a@a.com')
INSERT INTO @Table2 VALUES(02,'20,30,40,2','b@a.com')
INSERT INTO @Table2 VALUES(03,'30,20,10,2','c@a.com')
INSERT INTO @Table2 VALUES(04,'4,20,3,1','d@a.com')


SELECT A.T1ID,Name,
     Split.a.value('.', 'VARCHAR(100)') AS [SchoolId]  
INTO #T1Vals
 FROM  
 (
     SELECT T1ID,Name,
         CAST ('<M>' + REPLACE(SchoolIds, ',', '</M><M>') + '</M>' AS XML) AS Data  
     FROM  @Table1
 ) AS A CROSS APPLY Data.nodes ('/M') AS Split(a);

SELECT A.T2ID,Username,
     Split.a.value('.', 'VARCHAR(100)') AS [SchoolId]  
INTO #T2Vals
 FROM  
 (
     SELECT T2ID, Username,
         CAST ('<M>' + REPLACE(SchoolIds, ',', '</M><M>') + '</M>' AS XML) AS Data  
     FROM  @Table2
     WHERE Username='a@a.com'
 ) AS A CROSS APPLY Data.nodes ('/M') AS Split(a);

 SELECT * 
 FROM @Table1 
 WHERE T1ID IN(
    SELECT T1ID 
    FROM #T1Vals 
    WHERE [SchoolId] IN(SELECT [SchoolId] FROM #T2Vals))

 DROP TABLE #T1Vals
 DROP TABLE #T2Vals

Output:

T1ID    Name    SchoolIds
1       A       1,2,3,4
2       B       4,20,3,1
4       D       30,20,10,2