} else {
readIf("NULL");
}
if (readIf("CHECK")) {
Expression expr = readExpression();
column.addCheckConstraint(session, expr);
}
if (readIf("REFERENCES")) {
AlterTableAddConstraint ref = new AlterTableAddConstraint(session, schema, false);
ref.setConstraintName(constraintName);
ref.setType(AlterTableAddConstraint.REFERENTIAL);