-544 THE CHECK CONSTRAINT SPECIFIED IN THE ALTER TABLE STATEMENT CANNOT BE ADDED BECAUSE AN EXISTING ROW VIOLATES THE CHECK CONSTRAINT

Explanation
  An existing row violates the check constraint
specified in the ALTER TABLE statement.

System action
  The statement cannot be processed. The
check constraint definition is not added to the table. The table definition
is unchanged.

Programmer response
  Examine the check constraint definition
that was specified in the ALTER TABLE statement and the data in the
table to determine why the ALTER TABLE statement was rejected.
  You
can determine which rows violated the check constraint by using the
SELECT statement, negating the check constraint in the WHERE clause.
For example: SELECT * FROM table WHERE (NOT (check-condition));

SQLSTATE
  23512 