func (expr *Subquery) Walk(v Visitor) Expr {
	sel, changed := walkStmt(v, expr.Select)
	if changed {
		exprCopy := *expr
		exprCopy.Select = sel.(SelectStatement)
		return &exprCopy
	}
	return expr
}
// Walk implements the Expr interface.
Walk implements the Expr interface.
// Walk implements the Expr interface .
func (expr *Subquery) Walk(v Visitor) Expr {
	sel, changed := walkStmt(v, expr.Select)
	if changed {
		exprCopy := *expr
		exprCopy.Select = sel.(SelectStatement)
		return &exprCopy
	}
	return expr
}
func ( expr * Subquery ) Walk ( v Visitor ) Expr { sel , changed := walkStmt ( v , expr . Select ) if changed { exprCopy := * expr exprCopy . Select = sel . ( SelectStatement ) return & exprCopy } return expr }
Walk implements the Expr interface.
Walk implements the Expr interface .