How to select a subset of results from a select statement

Question

I have a table that stores RDF triples:

triples(triple_id, sub_id, pre_id, obj_id)

The method (I need to write) will receive an array of numbers which correspond to pre_id values. I want to select all sub_id values that have a corresponding pre_id for all the pre_ids in the array that is passed in.

E.g. if I had a single pre_id values passed in... lets call the value passed in preId, I would do:

select sub_id from triples where pre_id=preId;

However since I have mutliple pre_id values I want to keep iterating through the pre_id values and only keep the sub_id values corresponding to the "triples" records that have both.

E.g. image there are five records:

triples(1, 34,65,23)
triples(2, 31,35,28)
triples(3, 32,32,19)
triples(4, 12,65,28)
triples(5, 76,32,34)

If I pass in an array of pre_id values [65,32] then I want to select the first, third, fourth and fifth records.

What would I do for that?

Answer 1

This might not work with every database, but the keyword in can do this:

select sub_id from triples where pre_id in (65, 32)

Answer 2

You take in the incoming data as a single string, split it by delimiter, and put it into an @Table and use a JOIN, EXISTS or a sub query to get the rows back that you want.

Here is how to split a string into a @Table

T-SQL: Opposite to string concatenation - how to split string into multiple records

Fully working sample in SQL 2008

DROP FUNCTION dbo.Split
go
CREATE FUNCTION dbo.Split (@sep char(1), @s varchar(8000))
RETURNS table
AS
RETURN (
    WITH Pieces(pn, start, stop) AS (
      SELECT 1, 1, CHARINDEX(@sep, @s)
      UNION ALL
      SELECT pn + 1, stop + 1, CHARINDEX(@sep, @s, stop + 1)
      FROM Pieces
      WHERE stop > 0
    )
    SELECT pn,
      SUBSTRING(@s, start, CASE WHEN stop > 0 THEN stop-start ELSE 512 END) AS s
    FROM Pieces
  )
GO
Declare @Triples Table  
(
    triple_id Int, 
    sub_id VarChar (10),  
    pre_id VarChar (10),  
    obj_id VarChar (10)
)

INSERT INTO @Triples  VALUES
(1, 34,65,23),
(2, 31,35,28),
(3, 32,32,19),
(4, 12,65,28),
(5, 76,32,34)

SELECT * 
FROM @Triples Triples
    INNER JOIN dbo.split (',', '65,32') as InputValues
        ON Triples.pre_id = InputValues.S