Oracle PL/SQL/Constraints/Alter Constraints

Adding a check constraint that allows null values

 
SQL>
SQL>
SQL> CREATE TABLE product (
  2       product_name  VARCHAR2(25),
  3       product_price NUMBER(4,2),
  4       purchase_date DATE
  5       );
Table created.
SQL>
SQL> ALTER TABLE product ADD (
  2       CONSTRAINT reasonable_stock_date CHECK(
  3            TO_CHAR(purchase_date, "YYYY-MM-DD") >= "2001-12-31"
  4            )
  5       );
Table altered.
SQL>
SQL> INSERT INTO product VALUES ("S", 49, "30-DEC-01");
INSERT INTO product VALUES ("S", 49, "30-DEC-01")
*
ERROR at line 1:
ORA-02290: check constraint (sqle.REASONABLE_STOCK_DATE) violated

SQL>
SQL> drop table product;
Table dropped.
SQL>
SQL>