Thread: no value fetch
hi, Imagine that I have the following table where ts_sent is a timestamp(0) select * from notification; to_used | ts_sent | from ---------------------+-------------------------+--------- amanda@obs.unige.ch | 2004-07-21 14:19:43+02 | amanda amanda@obs.unige.ch | | postgres and so, how do I do to fetch the second line by asking : catch me the line where ts_sent doesn't have a value ! I've try: select * from notification where ts_sent = null ; without success... Anyone has an idea how to do this ? Thanks in advance ! Cedric BRINER
On Tue, 27 Jul 2004, BRINER Cedric wrote: > hi, > > Imagine that I have the following table where ts_sent is a timestamp(0) > > select * from notification; > to_used | ts_sent | from > ---------------------+-------------------------+--------- > amanda@obs.unige.ch | 2004-07-21 14:19:43+02 | amanda > amanda@obs.unige.ch | | postgres > > and so, how do I do to fetch the second line by asking : > catch me the line where ts_sent doesn't have a value ! > > I've try: > select * from notification where ts_sent = null ; Use ts_sent IS NULL, not ts_sent = null. Pretty much, <anything> = null returns null.
Stephan Szabo <sszabo@megazone.bigpanda.com> wrote: > > > On Tue, 27 Jul 2004, BRINER Cedric wrote: > > > hi, > > > > Imagine that I have the following table where ts_sent is a timestamp(0) > > > > select * from notification; > > to_used | ts_sent | from > > ---------------------+-------------------------+--------- > > amanda@obs.unige.ch | 2004-07-21 14:19:43+02 | amanda > > amanda@obs.unige.ch | | postgres > > > > and so, how do I do to fetch the second line by asking : > > catch me the line where ts_sent doesn't have a value ! > > > > I've try: > > select * from notification where ts_sent = null ; > > Use ts_sent IS NULL, not ts_sent = null. > > Pretty much, <anything> = null returns null. To expand on this... This is because NULL is nothing. Not zero, but *nothing*. Being nothing, it cannot "equal" anything. Not even itself. But a space can *contain* nothing. And it can contain "not nothing." Jim