SQL Server, Merge two records in one record - sql

Question

We have these tables
CREATE TABLE tbl01
(
[id] int NOT NULL PRIMARY KEY,
[name] nvarchar(50) NOT NULL
)
CREATE TABLE tbl02
(
[subId] int NOT NULL PRIMARY KEY ,
[id] int NOT NULL REFERENCES tbl01(id),
[val] nvarchar(50) NULL,
[code] int NULL
)
If we run this query:
SELECT
tbl01.id, tbl01.name, tbl02.val, tbl02.code
FROM
tbl01
INNER JOIN
tbl02 ON tbl01.id = tbl02.id
we get these results:
-------------------------------
id | name | val | code
-------------------------------
1 | one | FirstVal | 1
1 | one | SecondVal | 2
2 | two | YourVal | 1
2 | two | OurVal | 2
3 | three | NotVal | 1
3 | three | ThisVal | 2
-------------------------------
You can see that each two rows are related to same "id"
The question is: we need for each id to retrieve one record with all val, each val will return in column according to the value of column code
if(code = 1) then val as val-1
else if (code = 2) then val as val-2
Like this:
-------------------------------
id | name | val-1 | val-2
-------------------------------
1 | one | FirstVal | SecondVal
2 | two | YourVal | OurVal
3 | three | NotVal | ThisVal
-------------------------------
Any advice?

Answer 1

Use can use MAX and Group By to achieve this
SELECT id,
name,
MAX([val1]) [val-1],
MAX([val2]) [val-2]
FROM ( SELECT tbl01.id, tbl01.name,
CASE code
WHEN 1 THEN tbl02.val
ELSE ''
END [val1],
CASE code
WHEN 2 THEN tbl02.val
ELSE ''
END [val2]
FROM tbl01
INNER JOIN tbl02 ON tbl01.id = tbl02.id
) Tbl
GROUP BY id, name

Answer 2

Is it the PIVOT operator (http://technet.microsoft.com/en-us/library/ms177410(v=sql.105).aspx) that you are looking for?

Answer 3

You've already got a few answers, but heres one using PIVOT as an alternative. The good thing is this approach is easy to scale if there are additional columns required later
-- SETUP TABLES
DECLARE #t1 TABLE (
[id] int NOT NULL PRIMARY KEY,
[name] nvarchar(50) NOT NULL
)
DECLARE #t2 TABLE(
[subId] int NOT NULL PRIMARY KEY ,
[id] int NOT NULL,
[val] nvarchar(50) NULL,
[code] int NULL
)
-- SAMPLE DATA
INSERT #t1 ( id, name )
VALUES ( 1, 'one'), (2, 'two'), (3, 'three')
INSERT #t2
( subId, id, val, code )
VALUES ( 1,1,'FirstVal', 1), ( 2,1,'SecondVal', 2)
,( 3,2,'YourVal', 1), ( 4,2,'OurVal', 2)
,( 5,3,'NotVal', 1), ( 6,3,'ThisVal', 2)
-- SELECT (using PIVOT)
SELECT id, name, [1] AS 'val-1', [2] AS 'val-2'
FROM
(
SELECT t2.id, t1.name, t2.val, t2.code
FROM #t1 AS t1 JOIN #t2 AS t2 ON t2.id = t1.id
) AS src
PIVOT
(
MIN(val)
FOR code IN ([1], [2])
) AS pvt
results:
id name val-1 val-2
---------------------------------
1 one FirstVal SecondVal
2 two YourVal OurVal
3 three NotVal ThisVal

Answer 4

If there are always only two values, you could join them or even easier, group them:
SELECT tbl01.id as id, Min(tbl01.name) as name, MIN(tbl02.val) as val-1, MAX(tbl02.val) as val-2
FROM tbl01
INNER JOIN tbl02 ON tbl01.id = tbl02.id
GROUP BY tbl02.id
note: this query will always put the lowest value in the first column and highest in the second, if this is not wanted: use the join query:
Join query
If you always want code 1 in the first column and code 2 in the second:
SELECT tbl01.id as id, tbl01.name as name, tbl02.val as val-1, tbl03.val as val-2
FROM tbl01
INNER JOIN tbl02 ON tbl01.id = tbl02.id
ON tbl02.code = 1
INNER JOIN tbl03 ON tbl01.id = tbl03.id
ON tbl03.code = 2
Variable amount of columns
You cannot get an variable amount of columns, only when you do this by building your query in code or t-sql stored procedures.
My advice:
If its always to values: join them in query, if not, let your server-side code transform the data. (or even better, find a way which makes it not nessecery to transform data)

Answer 5

Try this - it uses a pivot function but it also creates creates the dynamic columns dependent on code
DECLARE #ColumnString varchar(200)
DECLARE #sql varchar(1000)
CREATE TABLE #ColumnValue
(
Value varchar(500)
)
INSERT INTO #ColumnValue (Value)
SELECT DISTINCT '[' + 'value' + Convert(Varchar(20),ROW_NUMBER() Over(Partition by id Order by id )) + ']'
FROM Test
SELECT #ColumnString = COALESCE(#ColumnString + ',', '') + Value
FROM #ColumnValue
Drop table #ColumnValue
SET #sql =
'
SELECT *
FROM
(
SELECT
id,name,val,''value'' + Convert(Varchar(20),ROW_NUMBER() Over(Partition by id Order by id ))as [values]
FROM Test
) AS P
PIVOT
(
MAX(val) FOR [values] IN ('+#ColumnString+')
) AS pv
'
--print #sql
EXEC (#sql)