RE: ESQL/C and test on NULL

Posted in 1999

William Raper — Thu, 14 Oct 1999 08:08:47 -0400 — source: Informix-list mailing list archive (1991-1998)

The concept of "EQUALS NULL" is not a valid concept in the Informix world. A DBMS NULL is not the same as a C NULL. This is because the value NULL is defined as "Unknown or Undefined". This is not only "Unknown or Undefined" in the data values, but also in the data types. This is why an EQUAL test is not valid on a NULL. I believe you will find this to be consistent across many other SQL-based DBMS systems. -----Original Message----- From: Pierre Henrotay [mailto:Pierre.Henrotay@skynet.be] Sent: Wednesday, October 13, 1999 4:08 PM To: informix-list@iiug.org Subject: ESQL/C and test on NULL 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