SQL 服务器/T-SQL: Return 来自构造的单个值 table

Question

我正在编写一个内联函数，它接受固定数量的参数（在代码示例中为 9 个），将这些参数排列成一个具有 2 列和 4 行的构造 table，对 table，然后 returns 来自所述 table 的单个值（第 1 列中的值，以及调用语句请求的第 1-4 行中的值）。

我已经完成了大部分。

但我需要知道如何 select 末尾的特定列和行索引。

您可能会问为什么我为此需要一个内联函数，答案是因为 a) 排序是至关重要的，b) 这是在内存优化的计算列中使用的 table , 不允许子查询等

这是我目前的代码：

CREATE FUNCTION [dbo].[SelectOrderedInputValue]
(
    -- 1-based row index of the desired return value
    @RequestedRowIndex INT,

    @InputValue1 INT,
    @InputValue2 INT,
    @InputValue3 INT,
    @InputValue4 INT,
    @InputRank1 INT,
    @InputRank2 INT,
    @InputRank3 INT,
    @InputRank4 INT
)
RETURNS TABLE AS RETURN
(
    /* Places the parameters into a table, and sorts by rank.

       I need to figure out how to specify a row and column,
       so I can return the single requested value from this table.

       In this case, I need to return the value in column #1 (alias InputValues)
       and row # @RequestedRowIndex*/

    SELECT TOP 4 InputValues FROM
    (VALUES
        ([InputValue1], [InputRank1]),
        ([InputValue2], [InputRank2]),
        ([InputValue3], [InputRank3]),
        ([InputValue4], [InputRank4])
    ) AS Inputs(InputValues, InputRanks) ORDER BY InputRanks ASC
)

Answer 1

试试 OFFSET FETCH

    DECLARE @RequestedRowIndex INT=4
    SELECT * FROM (
   SELECT TOP 4 * FROM
    (VALUES
        (10, 11),
        (20, 21),
        (30, 31),
        (40, 41)
    ) AS Inputs(InputValues, InputRanks) 
    ORDER BY InputRanks ASC )A 
    ORDER BY InputRanks ASC  
    OFFSET @RequestedRowIndex-1 ROWS FETCH NEXT 1 ROWS ONLY

Answer 2

没有必要为单个值 return table。只需使用标量函数：

CREATE FUNCTION [dbo].[SelectOrderedInputValue] (
    -- 1-based row index of the desired return value
    @RequestedRowIndex INT,

    @InputValue1 INT,
    @InputValue2 INT,
    @InputValue3 INT,
    @InputValue4 INT,
    @InputRank1 INT,
    @InputRank2 INT,
    @InputRank3 INT,
    @InputRank4 INT
) RETURNS INT AS
BEGIN
    /* Places the parameters into a table, and sorts by rank.

       I need to figure out how to specify a row and column,
       so I can return the single requested value from this table.

       In this case, I need to return the value in column #1 (alias InputValues)
       and row # @RequestedRowIndex*/
    DECLARE @retval INT;

    SET @retval = (SELECT TOP 4 *
                   FROM (VALUES ([InputValue1], [InputRank1]),
                                ([InputValue2], [InputRank2]),
                                ([InputValue3], [InputRank3]),
                                ([InputValue4], [InputRank4])
                        ) Inputs(InputValues, InputRanks)
                   ORDER BY InputRanks ASC
                   OFFSET @RequestedRowIndex-1 FETCH FIRST 1 ROW ONLY
                  );

    RETURN @retval;
END;

SQL 服务器/T-SQL: Return 来自构造的单个值 table

SQL Server / T-SQL: Return a single value from a constructed table

sql

sql-server

sql-server-2017