Re: How to check for NULL values in ISQL

>From: Sally Woolrich <Sally@excelsis.demon.co.uk> >Date: Fri, 13 Oct 95 14:36:40 GMT >X-Informix-List-Id: <news.17935> > >In article <45lo6u$aqc@hazel.Read.TASC.COM> > amiller@tasc.com "Andrew Miller" writes: > >> kcj@netcom.com (Kate Juliff) wrote: >> >> >How do I check for nulls in a column of type INTEGER? >> >> Use an indicator variable for the host variable you're selecting into. The >> indicator variable will contain -1 if the field is NULL. See the "Indicator >> Variables" section of "Programming with ESQL/C for Windows" for more details. > >This will show if the column *allows* NULLs, but not if it actually >*contains* NULLs. If the later is what is required, the data will >have to be searched in some manner. I presume that the date when Sally's answer was posted had something to do with the gremlins in it :-) On the contrary, the indicator variable indicates whether the current value is NULL or not; it does not indicate whether the column allows nulls or not, and that information is not readily available except by interrogating SysColumns and SysTables, a non-trivial exercise. DESCRIBE does not provide that information. Of course, the original question was about ISQL, so indicator variables are of minimal relevance anyway -- they apply to ESQL/C only (not even I4GL). I've seen a number of answers, most of which had some merit. I'd summarise the solutions as: * In SQL (or ACE): SELECT KeyData FROM SomeTable WHERE IntegerColumn IS NULL; * In Perform: Query on the column using just an equals sign as the query condition. Yours, Jonathan Leffler (johnl@informix.com) #include <disclaimer.h>