func (chk *CheckConstraint) Build() (sql string, vars []interface{}) {
	return "CONSTRAINT ? CHECK (?)", []interface{}{clause.Column{Name: chk.Name}, clause.Expr{SQL: chk.Constraint}}
}

// ParseCheckConstraints parse schema check constraints
func (schema *Schema) ParseCheckConstraints() map[string]CheckConstraint {
	checks := map[string]CheckConstraint{}
	for _, field := range schema.FieldsByDBName {