Re: Beginner, using IF/THEN/ELSE inside a CHECK clause ?

hi,

read this.

http://otn.oracle.com/docs/products/oracle9i/doc_library/901_doc/server.901/a90125/statements_412a.htm#2061500

CHECK Constraints
The CHECK clause lets you specify a condition that each row in the table must satisfy. To satisfy the constraint, each row in the table must make the condition either TRUE or unknown (due to a null). When Oracle evaluates a CHECK constraint condition for a particular row, any column names in the condition refer to the column values in that row.

If you create multiple CHECK constraints for a column, design them carefully so their purposes do not conflict, and do not assume any particular order of evaluation of the conditions. Oracle does not verify that CHECK conditions are not mutually exclusive.

See Also:
Chapter 5, "Conditions" for additional information and syntax    

Restrictions on CHECK Constraints

You cannot specify a CHECK constraint for a view.

The condition of a CHECK constraint can refer to any column in the table, but it cannot refer to columns of other tables.

CHECK constraint conditions cannot contain the following constructs:

Subqueries

Calls to the functions SYSDATE, UID, USER, or USERENV

The pseudocolumns CURRVAL, NEXTVAL, LEVEL, or ROWNUM

Date constants that are not fully specified Received on Wed Nov 06 2002 - 18:55:36 CET