I have three columns, and one of them can be null. I'd like to create a unique constraint across all three columns and allow only one null value. e.g. a|b|c abc|123|null abc|123|null # not allowed abc|456|null abc|456|987 abc|456|876 def|456|null def|456|null # not allowed Currently, the 'not allowed' lines are allowed. thanks csn __________________________________ Yahoo! for Good - Make a difference this year. http://brand.yahoo.com/cybergivingweek2005/
