Empty strings are NOT nulls. They are just zero length strings. Aron Pilhofer wrote:
>>Changing the column to allow NULL doesn't mean that any of the existing >>values will be *changed* to NULL. That seems to be what you're expecting, >>but why? >> > > >No, no. Maybe I didn't explain well enough. The fields in question contained >NULL values from the beginning, when I populated them, even though the >fields were set up not to allow NULLs. Is that clearer? > >If I had set up the table correctly from the beginning, there would be some >records with values, some with NULLs, in a field formatted to accept either >one. Since I didn't, one would think the insert would fail or something like >that -- but it didn't. MySQL populated the table just fine. And since NULLs >weren't allowed, it must have assigned some kind of invisible placeholder >value or something in those instances. I know it did something along these >lines because a count() should not have included NULLs, but it did. And a >select should of NULLs should have produced results, but it didn't. > >I realized my mistake, went back and fixed the field, but the count() and >select still produced the same results. Those placeholder values (and I'm >just guessing here that's what's going on) are not stripped out. > >The bottom line is this: If you create a field in which there will be NULL >values, you *must* create the table to allow NULLs from the beginning, even >though inserts and such appear to work. You cannot change the field to allow >NULLs after the fact and expect it to work correctly. > >What I am wondering is whether this is the expected, correct behavior or a >bug? Also, if there's any workaround that makes those blanks into true >NULLs? > >Hope that's clearer. Thanks in advance! > > >---------------------------------------------------- >: Aron Pilhofer >: Director, Campaign Finance Information Center >: Investigative Reporters and Editors >: National Institute for Computer-Assisted Reporting >~ >: Phone: (202) 362-3223 >: Email: [EMAIL PROTECTED] >:"SQL Forever" > > > > >--------------------------------------------------------------------- >Before posting, please check: > http://www.mysql.com/manual.php (the manual) > http://lists.mysql.com/ (the list archive) > >To request this thread, e-mail <[EMAIL PROTECTED]> >To unsubscribe, e-mail ><[EMAIL PROTECTED]> >Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php > > --------------------------------------------------------------------- Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
