Question

我有一个表函数，它接受2个参数并返回2列。为简单起见，我们调用函数Get_GroupNumber

Get_GroupNumber('Smith', '123-456-789')

这将再次返回2列，保持简单，说它是Reason1和Reason2

Reason1 = '111-222-333'
Reason2 = '555'666'777'

现在，我需要做的是传递Reason1，它返回到Get_GroupNumber，并继续这样做，直到它在Reason1中返回NULL并在Reason2中返回NULL。

所以，第二次调用看起来像这样

Get_GroupNumber('Smith','111-222-333')

有办法做到这一点吗？我正在使用SQL Server 2014

提前致谢

Answer 1

如果您不想使用迭代方法（例如，使用while循环），那么递归CTE可以完成这项工作。您可以阅读有关递归CTE here的更多信息，或查看此示例：

-- Here's a "dummy" function that has some hard-coded return values for illustrative
-- purposes. It will return ('111-222-333', '555-666-777') when it gets 123-456-789
-- as its second parameter, ('999-999-999', '000-000-000') when it gets 111-222-333
-- as its second parameter, and (null, null) otherwise.
create function Get_GroupNumber
(   
    @Param1 varchar(32),
    @Param2 varchar(32)
)
returns table
as
return 
(
    select
        Reason1 = case @Param2 when '123-456-789' then '111-222-333' when '111-222-333' then '999-999-999' else null end,
        Reason2 = case @Param2 when '123-456-789' then '555-666-777' when '111-222-333' then '000-000-000' else null end
);
go

-- The sample inputs from your question.
declare @Param1 varchar(32) = 'Smith';
declare @Param2 varchar(32) = '123-456-789';

-- And finally, the good stuff:
with GroupNumberCTE as
(
    -- Base case: pass the original parameters, get the results from the function, and
    -- create a new field called "Call #" that will illustrate the order in which the
    -- various calls to Get_GroupNumber were made. (This field is purely informational;
    -- you can remove it if you don't want it.)
    select 
        [Call #] = 1,
        Reason1, 
        Reason2 
    from 
        Get_GroupNumber(@Param1, @Param2)

    union all

    -- Recursive case: if the previous call returned a non-null value in either field,
    -- invoke the function again with the original @Param1 and the Reason1 from the
    -- previous call. 
    select
        [Call #] = [Previous].[Call #] + 1,
        [Next].Reason1,
        [Next].Reason2
    from
        GroupNumberCTE [Previous]
        cross apply Get_GroupNumber(@Param1, [Previous].Reason1) [Next]
    where
        [Previous].Reason1 is not null or
        [Previous].Reason2 is not null
)
select * from GroupNumberCTE;

结果集：

Call #   Reason1       Reason2
----------------------------------
1        111-222-333   555-666-777
2        999-999-999   000-000-000
3        NULL          NULL

我应该指出这里存在危险：我的CTE结构中没有任何东西可以保证递归最终会结束。因此，您必须确保对于任何可行的初始输入集，Get_GroupNumber的实现最终将返回两个空值。只要是这样，这种方法应该运作良好。

Answer 2

Using While Loop

DECLARE @key varchar(max);
DECLARE @retVal varchar(max);
SET @key = '123-456-789'
While @Key is not null
BEGIN
    set @retval = @key
    SET @key = (SELECT Return2 from [dbo].[Get_GroupNumber]('Smith',@key))
END;

print @retVal

我知道我只使用Return2列的返回值来测试

需要重复调用表函数

2 个答案:

需要重复调​​用表函数

2 个答案:

需要重复调用表函数