如何将单列拆分为多列

Question

I have a SQL Server table table_name like:

col1            col2
SomeString_1    23
SomeString_1    65
SomeString_1    300
SomeString_1    323

What I want to do is for one unique value in col1, I want to select all the values from col2 but each in it's own column.

So the query should be something like:

select col2 from table_name where col1 = 'SomeString_1';

But I need output in the form:

23  65  300 323

Basically each selected value should be in it's own column. So the result should always have one row and as many columns as the SomeString_1 is repeated.

I tried to search on SO but few questions I found had different conditions.

Answer 1

An approach can be applied by using FOR XML :

SELECT DISTINCT t.COL1, 
        (SELECT t1.COL2 + ' ' AS 'data()'
         FROM @TBL t1 
         WHERE t.COL1 = t1.COL1
         FOR XML PATH(''))
FROM @TBL t
WHERE t.COL1 = 'SomeString_1'

---

An example,

DECLARE @TBL TABLE (COL1 VARCHAR(100), COL2 VARCHAR(10))
INSERT INTO @TBL VALUES ('SomeString_1', '23'), 
                        ('SomeString_1', '65'), 
                        ('SomeString_1', '300'),
                        ('SomeString_1', '323')

SELECT DISTINCT t.COL1, 
        (SELECT t1.COL2 + ' ' AS 'data()'
         FROM @TBL t1 
         WHERE t.COL1 = t1.COL1
         FOR XML PATH(''))
FROM @TBL t
WHERE t.COL1 = 'SomeString_1'

which returns,

COL1            (No column name)
SomeString_1    23  65  300  323 

Answer 2

Seems like OP is asking for separate column value for each row value:

create table #Table1 (COL1 VARCHAR(100), COL2 VARCHAR(10))
INSERT INTO #Table1 VALUES ('SomeString_1', '23'), 
                          ('SomeString_1', '65'), 
                          ('SomeString_1', '300'),
                          ('SomeString_1', '323')

DECLARE @columns nvarchar(MAX) = STUFF((
SELECT DISTINCT ',[col-' + cast(row_number() over (order by (select 1)) as varchar(4))+']'
FROM #Table1
FOR XML PATH('')), 1, 1, '')

DECLARE @sql nvarchar(MAX) = N'
SELECT * FROM
(
    SELECT col2, ''col-'' + cast(row_number() over (order by (select 1)) as varchar(4)) as dupcol2
    FROM #Table1 where col1 = ''SomeString_1''
) T
PIVOT
(MAX(col2) FOR dupcol2 IN ('+@columns+')) P'

EXEC (@sql)

Output:

col-1 | col-2 | col-3 | col-4
------------------------------
23    | 65    | 300   | 323

Answer 3

You can use COALESCE also..

DECLARE @Names VARCHAR(8000) 

SELECT @Names = COALESCE(@Names + ' ', '') + COL2
FROM YourTable
WHERE COL1 = 'SomeString_1'

SELECT @Names