SQL Server 相當於 MySQL 中的 substring_index 函數

Question

我正在嘗試將查詢從 MySQL 移植到 SQL SERVER 2012。

我如何為 MySQL 的 substring_index() 編寫等價物？

MySQL SUBSTRING_INDEX()在指定的分隔符出現次數之前返回給定字符串中的子字符串。

SUBSTRING_INDEX(str, delim, count)

SELECT SUBSTRING_INDEX('www.somewebsite.com','.',2);

輸出： 'www.somewebsite'

Answer 1

試試這個基於 T-SQL 和 XQuery( (root/row)[position() <= sql:variable("@count")] ) 的解決方案：

T-SQL 標量函數：

CREATE FUNCTION dbo.SUBSTRING_INDEX
(
    @str NVARCHAR(4000),
    @delim NVARCHAR(1),
    @count INT
)
RETURNS NVARCHAR(4000)
WITH SCHEMABINDING
BEGIN
    DECLARE @XmlSourceString XML;
    SET @XmlSourceString = (SELECT N'<root><row>' + REPLACE( (SELECT @str AS '*' FOR XML PATH('')) , @delim, N'</row><row>' ) + N'</row></root>');

    RETURN STUFF
    (
        ((
            SELECT  @delim + x.XmlCol.value(N'(text())[1]', N'NVARCHAR(4000)') AS '*'
            FROM    @XmlSourceString.nodes(N'(root/row)[position() <= sql:variable("@count")]') x(XmlCol)
            FOR XML PATH(N''), TYPE
        ).value(N'.', N'NVARCHAR(4000)')), 
        1, 1, N''
    );
END
GO

SELECT dbo.SUBSTRING_INDEX(N'www.somewebsite.com', N'.', 2) AS Result;

輸出：

/*
Result
---------------
www.somewebsite
*/

或者

TSQL 內聯表值函數：

CREATE FUNCTION dbo.SUBSTRING_INDEX
(
    @str NVARCHAR(4000),
    @delim NVARCHAR(1),
    @count INT
)
RETURNS TABLE
AS 
RETURN
    WITH Base
    AS 
    (
        SELECT XmlSourceString = CONVERT(XML, (SELECT N'<root><row>' + REPLACE( (SELECT @str AS '*' FOR XML PATH('')) , @delim, N'</row><row>' ) + N'</row></root>'))
    )   
    SELECT STUFF
    (
        ((
            SELECT  @delim + x.XmlCol.value(N'(text())[1]', N'NVARCHAR(4000)') AS '*'
            FROM    Base b 
            CROSS APPLY b.XmlSourceString.nodes(N'(root/row)[position() <= sql:variable("@count")]') x(XmlCol)
            FOR XML PATH(N''), TYPE
        ).value(N'.', N'NVARCHAR(4000)')), 
        1, 1, N''
    ) AS Result;
GO

SELECT  *
FROM    (
    SELECT N'www.somewebsite.com' UNION ALL 
    SELECT N'www.yahoo.com' UNION ALL 
    SELECT N'www.outlook.com'
) a(Value)
CROSS APPLY dbo.SUBSTRING_INDEX(a.Value, N'.', 2) b;

輸出：

/*
Value               Result
------------------- ---------------
www.somewebsite.com www.somewebsite
www.yahoo.com       www.yahoo
www.outlook.com     www.outlook
*/

Answer 2

我最近需要這個，所以我寫了以下存儲函數。 最后是一堆測試，以確保它的運行與 MySql 函數完全一樣（在那里運行相同的測試后，預期的結果是從 MySql 復制的）：

-- Function to reproduce the useful functionality of SUBSTRING_INDEX from MySql
CREATE FUNCTION dbo.SUBSTRING_INDEX(@InString  NVARCHAR(Max),
                                    @Delimiter NVARCHAR(Max),
                                    @Count     INT)
RETURNS NVARCHAR(200)
AS
BEGIN
    DECLARE @Pos INT;
    DECLARE @DelimiterOffsets TABLE
    (
         i      INT IDENTITY(1, 1) NOT NULL,
         offset INT NOT NULL
    );

    -- If @Count is zero, we return '' as per spec
    IF @Count = 0
    BEGIN
        RETURN '';
    END;

    DECLARE @OrigLength      INT = LEN(@InString);
    DECLARE @DelimiterLength INT = LEN(@Delimiter);

    -- Prime the pump.
    SET @Pos = Charindex(@Delimiter, @InString, 1);

    -- If the delimiter does not exist in @InString, return the whole string
    IF @Pos = 0
    BEGIN
        RETURN @InString;
    END;

    -- Put all delimiter offsets into @DelimiterOffsets, they get numbered automatically.
    DECLARE @CurrentOffset INT = 0;
    WHILE @Pos > 0
    BEGIN
        SET @CurrentOffset = @Pos;

        INSERT INTO @DelimiterOffsets
                    (offset)
             VALUES (@CurrentOffset);

        SET @Pos = Charindex(@Delimiter, @InString, @CurrentOffset + @DelimiterLength);
    END;

    -- This number is guaranteed to be > 0.
    DECLARE @DelimitersFound INT = (SELECT Count(*) FROM @DelimiterOffsets);

    -- If they requested more delimiters than were found, return the whole string, as per spec.
    IF Abs(@Count) > @DelimitersFound
    BEGIN
        RETURN @InString;
    END;

    DECLARE @StartSubstring INT = 0;
    DECLARE @EndSubstring   INT = @OrigLength;

    -- OK, now return the part they requested
    IF @Count > 0
    BEGIN
        SET @EndSubstring = (SELECT offset 
                               FROM @DelimiterOffsets 
                              WHERE i = @Count);
    END
    ELSE
    BEGIN
        SET @StartSubstring = (SELECT offset + @DelimiterLength 
                                 FROM @DelimiterOffsets 
                                WHERE i = (@DelimitersFound + @Count + 1));
    END;

    RETURN Substring(@InString, @StartSubstring, @EndSubstring);
END; 

Go 

GRANT EXECUTE ON [dbo].SUBSTRING_INDEX TO PUBLIC;

-- Tests
DECLARE @TestResults TABLE (i int, answer nVarChar(MAX), expected nVarChar(MAX));

insert into @TestResults
select * from  
(
    (SELECT  1 as i, [dbo].SUBSTRING_INDEX(N'www.somewebsite.com', N'.', 2)    as r, 'www.somewebsite'     as e) UNION
    (SELECT  2 as i, [dbo].SUBSTRING_INDEX(N'www.yahoo.com', N'.', 2)          as r, 'www.yahoo'           as e) UNION
    (SELECT  3 as i, [dbo].SUBSTRING_INDEX(N'www.outlook.com', N'.', 2)        as r, 'www.outlook'         as e) UNION
    (SELECT  4 as i, [dbo].SUBSTRING_INDEX(N'www.somewebsite.com', N'.', -2)   as r, 'somewebsite.com'     as e) UNION
    (SELECT  5 as i, [dbo].SUBSTRING_INDEX(N'www.yahoo.com', N'.', -2)         as r, 'yahoo.com'           as e) UNION
    (SELECT  6 as i, [dbo].SUBSTRING_INDEX(N'www.outlook.com', N'.', -2)       as r, 'outlook.com'         as e) UNION
    (select  7 as i, [dbo].SUBSTRING_INDEX('hi.you.com','.',2)                 as r, 'hi.you'              as e) UNION
    (select  8 as i, [dbo].SUBSTRING_INDEX('hi.you.com','.',-1)                as r, 'com'                 as e) UNION
    (select  9 as i, [dbo].SUBSTRING_INDEX(N'prueba','ue',1)                   as r, 'pr'                  as e) UNION
    (select 10 as i, [dbo].SUBSTRING_INDEX(N'prueba','ue',-1)                  as r, 'ba'                  as e) UNION
    (select 11 as i, [dbo].SUBSTRING_INDEX(N'prueba','ue',0)                   as r, ''                    as e) UNION
    (SELECT 12 as i, [dbo].SUBSTRING_INDEX(N'wwwxxxoutlookxxxcom', N'xxx', 2)  as r, 'wwwxxxoutlook'       as e) UNION
    (SELECT 13 as i, [dbo].SUBSTRING_INDEX(N'wwwxxxoutlookxxxcom', N'xxx', -2) as r, 'outlookxxxcom'       as e) UNION
    (SELECT 14 as i, [dbo].SUBSTRING_INDEX(N'wwwxxxoutlookxxxcom', N'xxx', 5)  as r, 'wwwxxxoutlookxxxcom' as e) UNION
    (SELECT 15 as i, [dbo].SUBSTRING_INDEX(N'wwwxxxoutlookxxxcom', N'xxx', -5) as r, 'wwwxxxoutlookxxxcom' as e)
) as results;

select tr.i,
       tr.answer,
       tr.expected,
       CASE WHEN tr.answer = tr.expected THEN 'Test Succeeded' ELSE 'Test Failed' END testState
  from @TestResults tr
 order by i;

這是一個受Bogdan Sahlean的回答啟發的版本，使用 SQL Server 的 XML 功能進行解析和組合：

CREATE FUNCTION dbo.SUBSTRING_INDEX(@InString  NVARCHAR(Max),
                                    @Delimiter NVARCHAR(Max),
                                    @Count     INT)
RETURNS NVARCHAR(200)
AS
BEGIN
    -- If @Count is zero, we return '' as per spec
    IF @Count = 0
    BEGIN
        RETURN '';
    END;

    -- First we let the XML parser break up the string by @Delimiter.
    -- Each parsed value will be <piece>[text]</piece>.
    DECLARE @XmlSourceString XML = (select N'<piece>' + REPLACE( (SELECT @InString AS '*' FOR XML PATH('')) , @Delimiter, N'</piece><piece>' ) + N'</piece>');

    -- This will contain the final requested string.
    DECLARE @Results nVarChar(MAX);

    ;WITH Pieces(RowNumber, Piece) as
    (
        -- Take each node in @XmlSourceString, and return it with row numbers
        -- which will identify each piece and give us a handle to change the
        -- order, depending on the direction of search.
        SELECT  row_number() over(order by x.XmlCol) as RowNumber,
                @Delimiter + x.XmlCol.value(N'(text())[1]', N'NVARCHAR(MAX)') AS '*'
          FROM  @XmlSourceString.nodes(N'(piece)') x(XmlCol)
    ), orderedPieces(RowNumber, Piece) as
    (
        -- Order the pieces normally or reversed depending on whether they want
        -- the first @Count pieces or the last @Count pieces.
        select TOP (ABS(@Count)) 
               RowNumber, 
               Piece
          from Pieces
         ORDER BY CASE WHEN @Count < 0 THEN RowNumber END DESC ,
                  CASE WHEN @Count > 0 THEN RowNumber END ASC
    ), combinedPieces(result) as
    (
        -- Now combine the pieces back together, ordering them by
        -- the original order.  There will always
        -- be an extra @Delimiter on the front of the string.
        select CAST(Piece AS VARCHAR(100))
          from OrderedPieces
         order by RowNumber
           FOR XML PATH(N'')
    )
    -- Finally, strip off the extra delimiter using STUFF and store the string in @Results.
    select @Results = STUFF(result, 1, LEN(@Delimiter), '') from combinedPieces;

    return @Results;
END;

運行測試會產生以下結果：

i  answer              expected             testState
1  www.somewebsite     www.somewebsite      Test Succeeded
2  www.yahoo           www.yahoo            Test Succeeded
3  www.outlook         www.outlook          Test Succeeded
4  somewebsite.com     somewebsite.com      Test Succeeded
5  yahoo.com           yahoo.com            Test Succeeded
6  outlook.com         outlook.com          Test Succeeded
7  hi.you              hi.you               Test Succeeded
8  com                 com                  Test Succeeded
9  pr                  pr                   Test Succeeded
10 ba                  ba                   Test Succeeded
11                                          Test Succeeded
12 wwwxxxoutlook       wwwxxxoutlook        Test Succeeded
13 outlookxxxcom       outlookxxxcom        Test Succeeded
14 wwwxxxoutlookxxxcom wwwxxxoutlookxxxcom  Test Succeeded
15 wwwxxxoutlookxxxcom wwwxxxoutlookxxxcom  Test Succeeded

Answer 3

    CREATE FUNCTION FN_SUBSTRING_INDEX
    (
       @TEXTO NVARCHAR(200),
      @SUBSTRING_INDEX NVARCHAR(10),
       @DESPLAZAMIENTO INT
    )
    RETURNS NVARCHAR(200)
    AS

    BEGIN


        DECLARE @indiceSubstring INT
        DECLARE @RESULTADO NVARCHAR(200)
        SELECT @indiceSubstring = CHARINDEX(@SUBSTRING_INDEX,@TEXTO)

        IF @DESPLAZAMIENTO > 0
        BEGIN
            SELECT @RESULTADO=SUBSTRING(@TEXTO,@indiceSubstring+@DESPLAZAMIENTO+1,LEN(@TEXTO))
        END 
        ELSE
        BEGIN
            SELECT @RESULTADO=SUBSTRING(@TEXTO,0,@indiceSubstring-@DESPLAZAMIENTO-1)
        END 

    RETURN @RESULTADO
    END
    GO

向右選擇 dbo.FN_SUBSTRING_INDEX(N'prueba','ue',1);

向左選擇 dbo.FN_SUBSTRING_INDEX(N'prueba','ue',-1);

Answer 4

我最好的選擇是：

select substring(email,(charindex('@', email,1)+1),100) from yourtable;

假設 TLD.EXT 最多 100 個字符。 你可以隨心所欲地增加。

祝你好運

Answer 5

試試這個.....

CREATE FUNCTION SubString_Index
(
   @ExistingString NVARCHAR(200),
   @BreakPoint NVARCHAR(10),
   @number INT
)
RETURNS NVARCHAR(200)
AS
BEGIN
DECLARE @Count INT
DECLARE @Substring NVARCHAR(200)
DECLARE @ssubstring NVARCHAR(200)
SET @ssubstring=@ExistingString
DECLARE @scount INT
SET @scount=0
DECLARE @sscount INT
SET @sscount=0
WHILE(@number>@scount)
    BEGIN
            Select @Count=CHARINDEX(@BreakPoint,@ExistingString)
            Select @ExistingString=SUBSTRING(@ExistingString,@Count+1,LEN(@ExistingString))
            Select @scount=@scount+1 
            select @sscount=@sscount+@Count
    END

SELECT @Substring=SUBSTRING(@ssubstring,0,@sscount)

RETURN @Substring
END
GO


select dbo.SubStringIndex('hi.you.com','.',1)

Answer 6

這個 microsoft sql 函數與 mysql 中的 substring_index 函數完全一樣

/** This microsoft sql function Works exactly like substring_index function in mysql **/
  
CREATE FUNCTION SubString_Index
(
   @ExistingString NVARCHAR(MAX),
   @BreakPoint NVARCHAR(MAX),
   @number INT
)
RETURNS NVARCHAR(MAX)
AS
BEGIN
DECLARE @Count INT
DECLARE @SubstringLength INT
DECLARE @Substring NVARCHAR(MAX)
DECLARE @ssubstring NVARCHAR(MAX)
SET @ssubstring=@ExistingString
DECLARE @scount INT
SET @scount=0
DECLARE @sscount INT
SET @sscount=0
DECLARE @number2 INT
DECLARE @occurence INT
SET @occurence=LEN(@ExistingString) - LEN(REPLACE(@ExistingString, @BreakPoint, ''))
If @number<0
     BEGIN
        SET @number2= @occurence-(-1*@number)+1
     END
If @number>0
     BEGIN
        SET @number2=@number
     END
WHILE(@number2>@scount)
    BEGIN
            Select @Count=CHARINDEX(@BreakPoint,@ExistingString)
            Select @SubstringLength=@Count+LEN(@BreakPoint) 
            Select @ExistingString=SUBSTRING(@ExistingString,@SubstringLength,LEN(@ExistingString)-@Count)
            Select @scount=@scount+1 
            select @sscount=@sscount+@Count
    END
If @number<0
     BEGIN
        if (@number = -1) and (@sscount+LEN(@BreakPoint)) = (LEN(@ssubstring)+1)
            BEGIN
               SELECT @Substring=''
            END
        else if @occurence = 0
            BEGIN
               SELECT @Substring=''
            END
        else
            BEGIN
               SELECT @Substring=SUBSTRING(@ssubstring, @sscount+LEN(@BreakPoint), LEN(@ssubstring))
            END
     END
If @number>0
    if @occurence = 0
            BEGIN
               SELECT @Substring=''
            END
        else
            BEGIN
               SELECT @Substring=SUBSTRING(@ssubstring,0,@sscount)
            END

RETURN @Substring
END
GO

Answer 7

使用 Python 獲得指數 -2

use my_guitar_shop;
go  


EXEC sp_execute_external_script 
@language =N'Python',
@script=N'

import pandas as pd
import numpy as np
x = np.array(InputDataSet["email_address"], dtype = str)
broken = np.char.split(x, sep = ".")
OutputDataSet = pd.DataFrame([".".join(e[-2:]) if len(e)>2 else ".".join(e) for e in broken])
', 
@input_data_1 = N'SELECT email_address  from customers;'
WITH RESULT SETS(([indexed_email] nvarchar(250)));