Hopefully this is the right section and I've no idea how to title this. I'm new to sql. Getting to grips - slowly.
Need help please
I have a table WIRES with columns ID(key), WTYPE, WSIZE.
Also have a table PARTS with columns ID(key), PNAME, WIRES_ID
Then I do a
SELECT WIRES.WTYPE, WIRES.WSIZE, PARTS.PNAME
LEFT JOIN PARTS
ON WIRES.ID = PARTS.WIRES_ID
This correctly gives me a list of wires and part names using them.
I get null for PNAME when a wire has no using part. correct.
But how can i filter out all rows where PNAME is null but only when there is another row with matching WTYPE WSIZE pair which has a PNAME not null
WTYPE WSIZE PNAME CH 1 null <-- this line to be removed CH 1 Bolt TY 3 Nut etc. WTYPE WSIZE PNAME CH 1 null <-- this line NOT to be removed TY 3 Nut etc.