ESQL/C and test on NULL

Posted in 1999

Topics: Connectivity: ESQL/C, 4GL & Embedded SQL

Pierre Henrotay — Wed, 13 Oct 1999 22:08:24 +0200 — source: Informix-list mailing list archive (1991-1998)

Can someone explain the difference between: - SELECT ... FROM ... WHERE ... mycolumn IS NULL and - SELECT ... FROM ... WHERE .... mycolumn = $hostvar where hostval has been set to NULL appropriately via rsetnull? Pierre

↪ replying to Pierre Henrotay

Art S. Kagel — Thu, 14 Oct 1999 12:08:39 -0400 — source: Informix-list mailing list archive (1991-1998)

The clause "mycolumn = NULL" is ALWAYS FALSE. The ONLY valid way to filter for the value of a column being NULL (or not NULL) is "mycolumn IS NULL", "mycolumn IS NOT NULL", or "NOT mycolumn IS NULL". Art S. Kagel Pierre Henrotay wrote: > > Can someone explain the difference between: > - SELECT ... FROM ... WHERE ... mycolumn IS NULL > and > - SELECT ... FROM ... WHERE .... mycolumn = $hostvar > where hostval has been set to NULL appropriately via rsetnull? > > Pierre

Glossary

ESQL/C