SQL Server query - return null value if no match

Question

I'm running into a problem that I cannot figure out for some reason. I am trying to write a query that joins two tables, in which a match may not be found in a table. Such as:

SELECT 
    Table1.IDField, Table2.IDField
FROM 
    Table1
LEFT OUTER JOIN 
    Table2 ON Table1.PersonID = Table2.PersonID
WHERE 
    (Table1.IDField = '12345')
    AND (Table2.Category = 'Foo')

If there is no match in Table2 , it's not returning anything. However, I need it to just return a NULL for that column if there is no match and still return the value from Table1 .

I have changed up the JOIN with everything that I can think of, but to no avail.

Table2.Category can contain multiple other values, so doing a OR IS NULL type of deal won't work.

So, if there is no match for Table2.Category = 'Foo' , I am still needing it to return:

Table1 | Table2
----------------
 12345 |  NULL

Any suggestions?

Answer 1

Move the condition for table2 out of your WHERE clause and into your JOIN .

SELECT 
    Table1.IDField, Table2.IDField
FROM 
    Table1
LEFT OUTER JOIN Table2 
    ON Table1.PersonID = Table2.PersonID
    AND Table2.Category = 'Foo'
WHERE 
    Table1.IDField = '12345'

Answer 2

Try this:

LEFT OUTER JOIN
Table2 ON Table1.PesonID = Table2.PersonID
AND Table2.Category = 'Foo'

then delete the 'Foo' line from the WHERE clause

Answer 3

The problem isn't in the join per se, but in the requirement in the where clause that match table2. I've solved this with a where coalese(table2.category, 'Foo') = 'Foo'. That way if the table2 is null, it will still match.