That may work for a single field in a record that is NULL, but I'm trying to join two tables, and report the lines that do not have an entry in the second thus:
Question Table Q_id Question 1 Question 1 2 Question 2 3 Question 3 4 Question 4 Response Table R_id Member_id Q_id Response 1 1 1 Yes 2 1 3 No So, member 1 has answered questions 1 and 3 - I want to find how to get the q_ids of the remaining questions... Q_id 2 4 Something like: SELECT q.q_id FROM questions q, responses r WHERE q.q_id=r.q_id AND r.member_id='1' AND r.id=NULL % NB This doesn't work... :( Or maybe it's better by taking the questions they have done, SELECT q_id FROM responses where member='1' and somehow subtracting this from the complete list, SELECT q_id FROM questions Any clues? Robin "Frank Flynn" <[EMAIL PROTECTED]> wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Pretty easy really > > SELECT * FROM foo WHERE bar is NULL > > - DON'T use quotes "NULL" is a valid string it is not the same as NULL > - Some DBMS's allow you to say bar = NULL but technically this is wrong > because NULL is undefined and cannot be equal to anything not even another > NULL. > - Also "" is not NULL - be sure you blank fields are NULL and not "" > - A clever way to search for both "" and NULL in the same query is: > > SELECT * FROM foo WHERE NOT bar > "" > > This may not work in all DBMS's but give it a try; OR would work too. > > Good Luck, > Frank > > On 2/26/02 2:20 PM, "[EMAIL PROTECTED]" > <[EMAIL PROTECTED]> wrote: > > > From: "Robin McKenzie" <[EMAIL PROTECTED]> > > Date: Tue, 26 Feb 2002 21:49:00 -0000 > > To: [EMAIL PROTECTED] > > Subject: Finding records with NULL values > > > > > > > > I have a table of questions, and a table of responses (initially empty) > > which gets updated every time an answer is submitted, with the question > > number, member id and response. > > > > I wish to produce a SELECT query that will find the questions that haven't > > been answered by a particular member, i.e. a query that finds the questions > > that DO NOT have an entry in responses. How can I do this? > > > > Regards, > > > > Robin > > > > > -- > Frank Flynn > Poet, Artist & Mystic > > -- PHP Database Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php