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Results tagged with Search options user 180

A database concept used to represent missing, unknown or inapplicable data.

10
votes
Wikipedia's article on SQL Null has some interesting remarks about the NULL value, and as a database-agnostic answer, as long as you are aware of the potential affects of having NULL values for your …
answered Aug 30 '11 by Derek Downey
14
votes
2answers
I am probably being narrow minded, but if I create a foreign key constraint and a row gets updated or deleted, I lose that connection if the child table's column gets set to NULL. What is the purpose of intentionally keeping these orphaned rows? …
asked Aug 29 '11 by Derek Downey
2
votes
Have you looked into the SELECT INTO OUTFILE syntax? Here is a quote on the NULL string issue: If the FIELDS ESCAPED BY character is empty, no characters are escaped and NULL is output as NULL
answered Jul 18 '11 by Derek Downey
6
votes
(SELECT COUNT(*) FROM foo WHERE col1 = NEW.col1 AND col2 = NEW.col2 AND col3 IS NULL) > 0) THEN SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'Cannot insert this item due to unique … BEGIN IF (ISNULL(NEW.col3) AND (SELECT COUNT(*) FROM foo WHERE col1 = NEW.col1 AND col2 = NEW.col2 AND col3 IS NULL) > 0) THEN SET NEW='Error: Cannot insert this item due to unique constraint'; END IF; END$$ DELIMITER ; [sqlfiddle] …
answered Apr 26 '13 by Derek Downey