Practical SQL Handbook, The: Using SQL Variants, Fourth Edition

Changing Null Displays

If members of your audience are not database-literate, they might find NULL confusing and decide it means zero. You can prevent trouble by using a function to substitute a value for NULL. On Adaptive Server Anywhere, this function is COALESCE (with two arguments) or ISNULL.

COALESCE ( expr, value-to-substitute-if-null)

The type column in the titles table allows NULL. Here's how the data looks

SQL

select title_id, type
from titles
title_id type
======== ============
PC8888   popular_comp
BU1032   business
PS7777   psychology
PS3333   psychology
BU1111   business
MC2222   mod_cook
TC7777   trad_cook
TC4203   trad_cook
PC1035   popular_comp
BU2075   business
PS2091   psychology
PS2106   psychology
MC3021   mod_cook
TC3218   trad_cook
MC3026   (NULL) ...