Paul Ramsteijn
12-22-2002, 02:50 AM
Straight from the Oracle 9.1 docs (sql_reference.pdf):
Paul Ramsteijn.
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
wing wrote:
Hi, I am new in Oracle and have a query on how to add conditional constraint. Say, I have a simple table Demerit with three fields. Demerit(DEM_CODE, DEM_DES, POINTS) where DEM_CODE (N, 2) DEM_DES (C, 30) POINTS (N, 1) How to add the following constraint? All DEM_CODE should carry an integer POINT between 1 to 6 inclusive, and DEM_CODE greater than 20 should carry no more than 3 POINT. Thanks in advance of any ideas and inputs. Wing
Paul Ramsteijn.
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
wing wrote:
Hi, I am new in Oracle and have a query on how to add conditional constraint. Say, I have a simple table Demerit with three fields. Demerit(DEM_CODE, DEM_DES, POINTS) where DEM_CODE (N, 2) DEM_DES (C, 30) POINTS (N, 1) How to add the following constraint? All DEM_CODE should carry an integer POINT between 1 to 6 inclusive, and DEM_CODE greater than 20 should carry no more than 3 POINT. Thanks in advance of any ideas and inputs. Wing