PrimaryKey

[Nagham]

How can I know by a query if a column is a primary key or not

[Shuja Ali]

Which database are you using? In case of SQL 2000 you can use the stored proced sp_helpcontraint to find out which column in a particular table is a primary/foreign key. Something like this will display a list of contrainst for a table sp_helpconstraint TABLENAME, 'nomsg'

[cjard]

try and insert NULL into it (impossible to do to a pk field)

say what database youre using. we arent telepaths...