Is possible have different conditions for each row in a query?

Question

How I can select a set of rows where each row match a different condition?

Example:

Supposing I have a table with a column called name, I want the

Answer 1

This may be close to what your after... but I need to know where you're getting your values for A, B, C etc...

Select [insert your fields here]
FROM
(Select T1.Name, T1.Age, RowNum as t1RowNum from T T1 order by name) T1O
Full Outer JOIN 
(Select T2.Name, T2.Age, RowNum as T2rowNum From T T2 order By name) T2O
ON T1O.T1RowNum+1 = T2O.T2RowNum

Answer 2

you can, but probably not in a way you would want:

if your table has a numeric id field, that is incremented with each row, you can self join that table 3 times (lets say as "a", "b" and "c") and use the join condition a.id + 1 = b.id and b.id + 1 = c.id and put you filter in a where clause like: a.name = 'A' AND b.name = 'B' AND c.name = 'C'

but don't expect performance ...

Answer 3

I suppose you could do a sub query for each row, but it wouldn't perform well or scale well at all and would be hard to maintain.

Answer 4

Assuming that You know how to provide a row number to your rows (ROW_NUMBER() in SQL Server, for instance), You can create a lookup (match) table and join on it. See below for explanation:

LookupTable:

RowNum    Value
1         A
2         B
3         C

Your SourceTable source table (assuming You already added RowNum to it-in case You didn't, just introduce subquery for it (or CTE for SQL Server 2005 or newer):

RowNum Name
-----------
1      A
2      B
3      C
4      D

Now You need to inner join LookupTable with your SourceTable on LookupTable.RowNum = SourceTable.RowNum AND LookupTable.Name = SourceTable.Name. Then do a left join of this result with LookupTable on RowNum only. If there is LookupTable.RowNum IS NULL in final result then You know that there is no complete match on at least one row.

Here is code for joins:

SELECT T.*, LT2.RowNum AS Matched 
FROM LookupTable LT2
LEFT JOIN 
(
    SELECT ST.*
    FROM SourceTable ST
    INNER JOIN LookupTable LT ON LT.RowNum = ST.RowNum AND LT.Name = ST.Name
) T
    ON LT2.RowNum = T.RowNum

Result set of above query will contain rows with Matched IS NULL if row is not matching condition from LookupTable table.