Question

I have three tables in an Access DB.

Labs (ID, TestLab)
Standards (ID, Standard, Keywords)
LabStd (ID, LabID, StdID)

A lab has many standards. Prior to today all I needed to do was match a search phrase to the keyword or standard columns in the Standards table.

Select Labs.ID, Labs.TestLab, Standards.standard
FROM Standards INNER JOIN (Labs INNER JOIN LabStd 
    ON Labs.ID = LabStd.LabID)
  ON Standards.ID = LabStd.StdID 
WHERE Standards.Keywords LIKE "%labstandard%"
OR Standards.standard LIKE "%labstandard%"
ORDER BY Labs.id, Standards.ID

Now, if a plus sign is used in the search (labstandard1+labstandard2) I need to split the string and see if a lab matches all the standards in the search. I figure I need to use a subquery for this and tried to use multiple WHERE IN statements but that doesn’t work so I’m at a loss.

As a test I removed the LIKE statements and just went to equals. The following query returns no results even though there is a matching standard for each and a lab associated with both standards.

SELECT Labs.ID, Labs.TestLab, Standards.standard
FROM Standards INNER JOIN (Labs INNER JOIN LabStd 
    ON Labs.ID = LabStd.LabID) 
ON Standards.ID = LabStd.StdID 
WHERE LabStd.StdID IN 
    (SELECT ID AS StdID FROM Standards 
     WHERE (Standards.Keywords = 'labstandard1' 
     OR Standards.standard ='labstandard1')
    ) 
AND LabStd.StdID IN 
    (SELECT ID as StdID 
     FROM Standards
     WHERE (Standards.Keywords = 'labstandard2'
            OR Standards.standard ='labstandard2')
    ) 
ORDER BY Labs.id, Standards.ID

I hope I explained that clear enough, let me know if I need to clarify anything.

Answer 1

The problem with your last query is that you’re looking for a single LabStd row where StdId is in both subsets, and that isn’t possible. What you want is to find all the Labs for which both standards exist. Someething like this:

SELECT 
    *
FROM
    Labs
WHERE
    EXISTS (
        SELECT
            1
        FROM
            LabStd INNER JOIN Standards ON LabStd.StdId = Standards.Id
        WHERE
            LabStd.LabId = Labs.Id
            AND
            ( Standards.Standard = 'labstandard1' or Standards.Keywords = 'labstandard1' )
    )
    AND
    EXISTS (
        SELECT
            1
        FROM
            LabStd INNER JOIN Standards ON LabStd.StdId = Standards.Id
        WHERE
            LabStd.LabId = Labs.Id
            AND
            ( Standards.Standard = 'labstandard2' or Standards.Keywords = 'labstandard2' )
    )