存储过程执行有误，请进来看具体情况

/************************购物车生成订单并支付[gen_order_cart]******************/
alter procedure gen_order_cart
@UserName    varchar(14)
as
    declare
    @balance float,    --用户余额
    @pay float,        --购物车总价
    @flag1 int,        --操作成功标志
    @flag2 int,
    @flag3 int;
    
    --获取账户余额
    select @balance=Balance from Member where UserName=@UserName;
    if @balance is null
    begin
        print '账户余额为空';
        return;
    end
    
    --获取购物车总价
    select @pay=sum(TmpPrice) from (select TmpPrice from Cart,TmpDetail 
        where Cart.TmpID=TmpDetail.TmpID and UserName=@UserName) as T;
    if @pay is null
    begin
        print '购物车为空';
        return;
    end

    --判断账户余额是否足以支付购物车中项目
    if @balance<@pay
    begin
        print '余额不足以支付';
        return;
    end
    
    --删除购物车项目并扣除账户余额，同时添加订单记录
    set @flag1=1;
    set @flag2=1;    
    set @flag3=1;
    BEGIN TRANSACTION
        --删除购物车项目
        delete from Cart where UserName=@UserName;
        print '用户['+@UserName+']购物车已经清空';    
        if @@rowcount=0
            set @flag1=0;
    
        --添加订单记录
        insert into "Order" (UserName,TmpID,PayTime) (select UserName,TmpID,getdate() from Cart where UserName=@UserName);
        print '用户['+@UserName+']购买记录已经添加';
        if @@rowcount=0
            set @flag2=0;

        --扣除账户余额
        update Member set Balance=(Balance-@pay) where UserName=@UserName;
        print '用户['+@UserName+']余额已经扣除';
        if @@rowcount=0
            set @flag3=0;

        --处理操作结果标识
        if @flag1=0 or @flag2=0 or @flag3=0
            ROLLBACK TRANSACTION;
        else
            COMMIT TRANSACTION;
go

--添加订单记录
        insert into "Order" (UserName,TmpID,PayTime) (select UserName,TmpID,getdate() from Cart where UserName=@UserName);
        print '用户['+@UserName+']购买记录已经添加';
        if @@rowcount=0
            set @flag2=0;

  insert into "Order" (UserName,TmpID,PayTime) (select UserName,TmpID,getdate() from Cart where UserName='abcabc');