Question

我需要在ntext列中提取诸如'％don％'之类的单词之前和之后的单词。

table A, column name: Text

示例：文字

where it was done it will retrieve the... at the end of the trip clare done everything to improve it is the only one done in these times

我想要以下结果：

was done it clare done everything one done in

我正在使用T-SQL，Left和right函数不适用于包含文本的列的ntext数据类型。

Answer 1

正如其他人所说，您可以使用字符串拆分功能将每个单词拆分出来，然后返回所需的单词。使用先前链接的DelimitedSplit8K：

CREATE FUNCTION dbo.DelimitedSplit8K
--===== Define I/O parameters
        (@pString VARCHAR(8000), @pDelimiter CHAR(1))
--WARNING!!! DO NOT USE MAX DATA-TYPES HERE!  IT WILL KILL PERFORMANCE!
RETURNS TABLE WITH SCHEMABINDING AS
 RETURN
--===== "Inline" CTE Driven "Tally Table" produces values from 1 up to 10,000...
     -- enough to cover VARCHAR(8000)
  WITH E1(N) AS (
                 SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
                 SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
                 SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1
                ),                          --10E+1 or 10 rows
       E2(N) AS (SELECT 1 FROM E1 a, E1 b), --10E+2 or 100 rows
       E4(N) AS (SELECT 1 FROM E2 a, E2 b), --10E+4 or 10,000 rows max
 cteTally(N) AS (--==== This provides the "base" CTE and limits the number of rows right up front
                     -- for both a performance gain and prevention of accidental "overruns"
                 SELECT TOP (ISNULL(DATALENGTH(@pString),0)) ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) FROM E4
                ),
cteStart(N1) AS (--==== This returns N+1 (starting position of each "element" just once for each delimiter)
                 SELECT 1 UNION ALL
                 SELECT t.N+1 FROM cteTally t WHERE SUBSTRING(@pString,t.N,1) = @pDelimiter
                ),
cteLen(N1,L1) AS(--==== Return start and length (for use in substring)
                 SELECT s.N1,
                        ISNULL(NULLIF(CHARINDEX(@pDelimiter,@pString,s.N1),0)-s.N1,8000)
                   FROM cteStart s
                )
--===== Do the actual split. The ISNULL/NULLIF combo handles the length for the final element when no delimiter is found.
 SELECT ItemNumber = ROW_NUMBER() OVER(ORDER BY l.N1),
        Item       = SUBSTRING(@pString, l.N1, l.L1)
   FROM cteLen l
;
go

declare @t table (t ntext);
insert into @t values('where it was done it will retrieve the...'),('at the end of the trip clare done everything to improve'),('we don''t take donut donations here'),('ending in don');

with t as (select cast(t as nvarchar(max)) as t from @t)
    ,d as (select t.t
                 ,case when patindex('%don%',s.Item) > 0 then 1 else 0 end as d
                 ,s.ItemNumber as i
                 ,lag(s.Item,1,'') over (partition by t.t order by s.ItemNumber) + ' '
                  + s.Item + ' '
                  + lead(s.Item,1,'') over (partition by t.t order by s.ItemNumber) as r
           from t
               cross apply dbo.DelimitedSplit8K(t.t, ' ') as s
          )
select t
      ,r
from d
where d = 1
order by t
        ,i;

输出：

+---------------------------------------------------------+-----------------------+
|                            t                            |           r           |
+---------------------------------------------------------+-----------------------+
| at the end of the trip clare done everything to improve | clare done everything |
| ending in don                                           | in don                |
| we don't take donut donations here                      | we don't take         |
| we don't take donut donations here                      | take donut donations  |
| we don't take donut donations here                      | donut donations here  |
| where it was done it will retrieve the...               | was done it           |
+---------------------------------------------------------+-----------------------+

还有一个可行的例子：

http://rextester.com/RND43071

提取特定单词之前和之后的单词

1 个答案: