// Expr returns clause.Expr, which can be used to pass SQL expression as params
func Expr(expr string, args ...interface{}) clause.Expr {
	return clause.Expr{SQL: expr, Vars: args}
}

// SetupJoinTable setup join table schema
func (db *DB) SetupJoinTable(model interface{}, field string, joinTable interface{}) error {
	var (
		tx                      = db.getInstance()
		stmt                    = tx.Statement

		Name          string
		Organizations []Organization `gorm:"many2many:region_orgs;"`
	}
	type RegionOrg struct {
		RegionId       uint
		OrganizationId uint
		Empty          myType
	}
	if err := DB.SetupJoinTable(&Region{}, "Organizations", &RegionOrg{}); err != nil {
		t.Fatalf("Failed to set up join table, got error: %s", err)
	}
	if err := DB.Migrator().DropTable(&Organization{}, &Region{}); err != nil {