Combine multiple SQL fields into 1 output row - sql

Question

Having a SQL table like
UserID |Attribute | Value
1 |Username | Marius
1 |Password | Fubar
I want to create an output like:
1 | Marius | Fubar
Maybe I'm just too tired to see it, doesn't sound too complicated, but I just can't seem to figure it out. Any help is appreciated.

Answer 1

Why don't you use self joins, ie. :
select u1.userid, u1.value, u2.value
from yourtable u1
inner join yourtable u2 on u2.userid=u1.userid
where u1.attribute='Username' and u2.attribute='Password';

Answer 2

Would something like...
SELECT userID,
GROUP_CONCAT (Value SEPARATOR '|')
FROM my_table
GROUP BY UserID;
be what you are looking for?

Answer 3

If you keep your data that way, you will need to do a crosstab query and pivot your rows into columns. If you are using Microsoft SQL Server, check out "crosstab query" and the pivot operator in Books Online.

Answer 4

Edited:
One column per result:
If you try to combine multiple Attributes with the same UserID it would be something like this:
Short query (one UserID):
declare #concattedtext varchar(1000)
SELECT #concattedtext=coalesce(#concattedtext + '|', '') + Value
FROM #users WHERE UserID=1
SELECT #concattedtext
RESULT with your example data:
1 | Marius | Fubar
Full query (all UserID's)
-- Your source table
CREATE Table #users (UserID int, Attribute varchar(50), Value varchar(50))
-- some entries
INSERT into #users (UserID, Attribute, Value)
VALUES (1, 'Test1', 'attr1')
INSERT into #users (UserID, Attribute, Value)
VALUES (1, 'Test2', 'attr2')
INSERT into #users (UserID, Attribute, Value)
VALUES (1, 'Test3', 'attr3')
INSERT into #users (UserID, Attribute, Value)
VALUES (2, 'Test4', 'attr4')
-- ids table variable (for distinct UserID's)
DECLARE #ids TABLE
(
rownum int IDENTITY (1, 1) Primary key NOT NULL,
UserID int
)
-- Output table variable
DECLARE #out TABLE
(
rownum int IDENTITY (1, 1) Primary key NOT NULL,
UserID int,
ConcatText varchar(1000)
)
-- get distinct id's
INSERT INTO #ids(UserID)
SELECT DISTINCT(UserID) FROM #users
-- Foreach vars
declare #RowCnt int
declare #MaxRows int
select #RowCnt = 1
select #MaxRows=count(*) from #ids
-- UserID
declare #id int
declare #concattedtext varchar(1000)
-- process each id
while #RowCnt <= #MaxRows
begin
SET #id = 0
SELECT #id=UserID
FROM #ids WHERE rownum=#RowCnt
SET #concattedtext = CONVERT(nvarchar(50), #id)
FROM #ids WHERE rownum=#RowCnt
SELECT #concattedtext=coalesce(#concattedtext + '|', '') + Value
FROM #users WHERE UserID=#id
INSERT INTO #out(UserID, ConcatText)
VALUES (#id, #concattedtext)
-- next UserID
Select #RowCnt = #RowCnt + 1
end
SELECT * FROM #out
DROP TABLE #users
Result:
rownum|UserID|ConcatTex
1 | 1 |1|attr1|attr2|attr3
2 | 2 |2|attr4
DROP TABLE #users
You might need a sort field to get your parameters in your requested order.
Multiple columns
Your data needs to have an equal count of attributes if you like to get a table with multiple columns. And you still need to take care about the ordering.
In this case a hardcoded query with a group by would be your choice.