Обсуждение: how can I query for unset timestamps
I have a table that I recently altered by adding several timestamp columns. I would like to query the table for those rows for which the timestamp has not been set but am unable to find a way to do so. any tips ? in psql the column appears empty and char_length returns nothing. Some of what I have tried "" -> not valid char_length(last_timestamp) > 0 -> returns the rows with the time stamps where NOT char_length(last_timestamp) > 0 -> returns 0 rows where NOT (char_length(last_timestamp) > 0 ) -> returns 0 rows where last_timestamp = NULL; -> 0 rows this is kicking my butt, and starting to piss me off so if any one has tips I would appreciate it. Bret
Bret -- A test for NULL uses the IS statement, e.g.: SELECT * FROM tablefoo WHERE last_timestamp IS NULL; HTH, Greg Williamson DBA GlobeXPlorer LLC -----Original Message----- From: Bret Hughes [mailto:bhughes@elevating.com] Sent: Tue 2/22/2005 1:09 PM To: postgresql sql list Cc: Subject: [SQL] how can I query for unset timestamps I have a table that I recently altered by adding several timestamp columns. I would like to query the table for those rows for which the timestamp has not been set but am unable to find a way to do so. any tips ? in psql the column appears empty and char_length returns nothing. Some of what I have tried "" -> not valid char_length(last_timestamp) > 0 -> returns the rows with the time stamps where NOT char_length(last_timestamp) > 0 -> returns 0 rows where NOT (char_length(last_timestamp) > 0 ) -> returns 0 rows where last_timestamp = NULL; -> 0 rows this is kicking my butt, and starting to piss me off so if any one has tips I would appreciate it. Bret ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster !DSPAM:421b9fba271461201672223!
Well, thank you very much. works perfectly, I guess I have not done much NULL value stuff. Bret On Tue, 2005-02-22 at 15:19, Gregory S. Williamson wrote: > Bret -- > A test for NULL uses the IS statement, e.g.: > > SELECT * FROM tablefoo WHERE last_timestamp IS NULL; > > HTH, > > Greg Williamson > DBA > GlobeXPlorer LLC > > -----Original Message----- > From: Bret Hughes [mailto:bhughes@elevating.com] > Sent: Tue 2/22/2005 1:09 PM > To: postgresql sql list > Cc: > Subject: [SQL] how can I query for unset timestamps > I have a table that I recently altered by adding several timestamp > columns. I would like to query the table for those rows for which the > timestamp has not been set but am unable to find a way to do so. any > tips ? in psql the column appears empty and char_length returns > nothing. > > Some of what I have tried > > "" -> not valid > > char_length(last_timestamp) > 0 -> returns the rows with the time > stamps > > where NOT char_length(last_timestamp) > 0 -> returns 0 rows > > where NOT (char_length(last_timestamp) > 0 ) -> returns 0 rows > > where last_timestamp = NULL; -> 0 rows > > this is kicking my butt, and starting to piss me off so if any one has > tips I would appreciate it. > > Bret > > > > > ---------------------------(end of broadcast)--------------------------- > TIP 4: Don't 'kill -9' the postmaster > > !DSPAM:421b9fba271461201672223! > > > > > > ---------------------------(end of broadcast)--------------------------- > TIP 7: don't forget to increase your free space map settings