How to group a couple of rows in SQL Server? - sql-server

Question

I have this query:
SELECT
Table1.ID, Table1.Code1, Table1.Code2, Table1.Details,
Table1.IDS, Table2.Name
FROM
Table1
INNER JOIN
Table2 ON Table1.Code1 = Table2.Code1
WHERE
Table1.IDS = 1
ORDER BY
Table1.Code1, Table1.Code2
This is my result for query:
ID Code1 Code2 Details IDS Name
1 1001 01 D1 1 N1
2 1001 01 D2 1 N1
3 1001 02 D3 1 N1
4 1001 05 D4 1 N1
5 1002 11 D5 1 N2
6 1002 12 D6 1 N2
7 1005 21 D7 1 N3
8 1005 21 D8 1 N3
But I want this result:
ID Code1 Code2 Details IDS Name
1 1001 01 D1 1 N1
2 01 D2 1
3 02 D3 1
4 05 D4 1
5 1002 11 D5 1 N2
6 12 D6 1
7 1005 21 D7 1 N3
8 21 D8 1
How do I get this result? Please help me. Thanks a lot

Answer 1

Embedding presentation logic in your query isn't ideal. I recommend you process the query results programmatically, either to detect when groups change as you iterate, or to transform the query results into a nested table. The latter can be generalized as a reusable function.

Answer 2

If you can rely on the ID column for ordering the groups (or a combination of other rows, like code1,code2) then you can do this in a few different ways.
If your server is 2012+ then you can use the LAG() window function to access previous rows and if the previous rows Code1 is the same as the current rows Code1 replace it with null (or an empty string if that suits you better). However, if you're using a version < 2012 then you can accomplish it using a self join.
This kind of formatting might be better to handle on the client side (or reporting layer) though if can.
The query below includes both versions, but I commented out the self-join stuff:
SELECT
Table1.ID,
-- CASE WHEN Table1.Code1 = t1.Code1 THEN NULL ELSE Table1.Code1 END AS Code1,
CASE WHEN LAG(Table1.Code1) OVER (ORDER BY Table1.ID) = Table1.Code1 THEN NULL ELSE Table1.Code1 END AS Code1,
Table1.Code2, Table1.Details, Table1.IDS,
-- CASE WHEN Table1.Name = t1.Name THEN NULL ELSE Table1.Name END AS Name,
CASE WHEN LAG(Table2.Name) OVER (ORDER BY Table1.ID) = Table2.Name THEN NULL ELSE Table2.Name END AS Name
FROM
Table1
INNER JOIN
Table2 ON Table1.Code1 = Table2.Code1
-- LEFT JOIN Table1 t1 ON Table1.ID = t1.ID + 1
WHERE
Table1.IDS = 1
ORDER BY
Table1.Code1, Table1.Code2
Sample SQL Fiddle

Answer 3

Morteza,
This is a clear case of a presentation/UI layer requirement. Databases are made for a particular purpose and that is to crunch data and present you with results. I'd highly recommend you to turn to the front end logic for achieving your purpose.

Answer 4

Using ROW_NUMBER() within CTE or a subquery, here is one way to get your expected output:
;WITH q1 as
(
SELECT
t1.ID,
t1.Code1,
t1.Code2,
t1.Details,
t1.IDS,
t2.Name,
ROW_NUMBER() OVER (PARTITION BY t1.Code1 ORDER BY t1.ID) as rn
FROM
table1 t1
INNER JOIN
Table2 t2 ON t1.Code1 = t2.Code1
)
SELECT
q1.ID,
CASE
WHEN rn = 1 THEN q1.Code1
ELSE ''
END as Code1, --only populate first row for each code1
q1.Code2,
q1.Details,
q1.IDS,
CASE
WHEN rn = 1 THEN q1.Name
ELSE ''
END as Name --only populate first row for each name
FROM
q1
WHERE
q1.IDS = 1
ORDER BY
q1.Code1, q1.Code2
SQL Fiddle Demo