使用SUBSTRING和CHARINDEX获取字段中的最后一个完整字

Question

我的数据库中有一个字段，为了报告目的，我打算使用下面的语句将其截断为50个字符。

SELECT (CASE WHEN (LEN(Notes) > 50) THEN SUBSTRING(Notes, 0, 50) + '...' WHEN (LEN(Notes) < 50) THEN SUBSTRING(Notes, 0, LEN(Notes)) + '...' ELSE 'NO NOTES WERE ENTERED' END) AS Notes FROM MyTable 

这个伟大的工程，但是，我想完成在备注字段的最后一个字，这样一个词是不切断，所以我想用CHARINDEX，SUBSTRING，扭转和可能正确的函数返回大约50个字符长度的字符串中最后一个完整的单词。

我已经尝试过，没有多少运气。

任何帮助，将不胜感激。

Answer 1

如果笔记列的长度超过50，则可以使用CHARINDEX查找位置50之后的下一个空格，并找到该位置的SUBSTRING。这是一个SQL Fiddle。

SELECT RTRIM(
    CASE 
     -- when the length is less than 50, or the character at position 50 is part of the last word, return the entire string 
     WHEN LEN(notes) < 50 OR (SUBSTRING(notes,50,1) <> ' ' AND CHARINDEX(' ',notes,50) = 0) 
      THEN notes 
     -- when the character at position 50 is a space, return the first 50 characters of the string 
     WHEN SUBSTRING(notes,50,1) = ' ' 
      THEN LEFT(notes, 50) 
     -- when the character at position 50 is a word, cut off the string at the next space after 50 
     WHEN SUBSTRING(notes,50,1) <> ' ' 
      THEN LEFT(notes,CHARINDEX(' ',notes,50)) 
    END) AS first_50 
FROM tbl_notes 

Answer 2

如果你不想超出字符数限制，你可以有这样的：

DECLARE @Table TABLE 
(
    String nvarchar(100) 
) 

DECLARE 
    @Size int    = 25 

INSERT @Table SELECT 'Lorem ipsum dolor sit ame' 
INSERT @Table SELECT 'Lorem ipsum dolor sit ame tas' 
INSERT @Table SELECT 'Lorem ipsum dolor sit am asd' 
INSERT @Table SELECT 'Lorem ipsum dolor sita am' 
INSERT @Table SELECT 'Lorem ipsum dolor sita a amet, consectetur adipiscing elit,' 
INSERT @Table SELECT 'Lorem ipsum dolor sita' 
INSERT @Table SELECT 'Lorem ipsum dolor sita asamet, consectetur adipiscing elit,' 

SELECT 
    LEN(R.LimitTruncation) AS LimitTruncationLen, 
    R.LimitTruncation, 
    LEN(String) AS StringLen, 
    R.String 
FROM 
(
    SELECT 
    String, 
    --This is the main part 
    CASE 
     WHEN LEN(String) <= @Size THEN String 
     WHEN CHARINDEX(' ', String, @Size) = @Size OR CHARINDEX(' ', String, @Size) = @Size + 1 THEN RTRIM(LEFT(String, @Size)) 
     ELSE REVERSE(SUBSTRING(REVERSE(LEFT(String, @Size)), CHARINDEX(' ', REVERSE(LEFT(String, @Size))), @Size)) 
    END AS LimitTruncation 
    FROM 
    @Table 
) R