CHARINDEX继续返回0

Question

有没有人知道为什么我仍然得到0由于:

SELECT [KnowItAll].[dbo].[VSM_CanculateTermFrequency] (
    'hello hi hello by hello why'
    ,'hi')
GO

哪里有VSM_CanculateTermFrequency:

CREATE FUNCTION [dbo].[VSM_CanculateTermFrequency] 
(
    @i_Document NCHAR(4000),
    @i_Term NCHAR(30)
)
RETURNS SMALLINT
AS
BEGIN
    -- Declare the return variable here
    DECLARE @TermFrequency    SMALLINT
    DECLARE @pos              INT
    DECLARE @nextpos          INT

    SELECT @pos = 0, @nextpos = 1, @TermFrequency = 0

    WHILE @nextpos > 0
    BEGIN
        SELECT @nextpos = CHARINDEX(@i_Term,@i_Document)
        SELECT @TermFrequency = CASE
                                    WHEN @nextpos > 0 THEN @TermFrequency + 1
                                    ELSE @TermFrequency
                                END
        SELECT @pos = @nextpos
    END
    RETURN @TermFrequency
END

Answer 1

问题是你的使用nchar.实际上,你没有搜索'hi',你正在寻找

'hi                            '

您应该将两个参数的数据类型更改为nvarchar.通过使用nchar,系统用空格填充值,使其变为30或4000个字符.

顺便说一句,我看到与CharIndex无关的另一个问题总是返回零问题(这是由于填充),是你没有告诉CharIndex在最后找到的术语后搜索.您应该将对CharIndex的调用更改为:

CHARINDEX(@i_Term,@i_Document,@pos + 1)

(顺便说一句,我看到Gabe首先发现了这个)