SQL：在字符串中查找连续的重复字符

Question

我试图在使用SQL Server的列中查找4个或更多个连续的重复字符。任何帮助，将不胜感激。

我的数据：

CompanyName 
HSBC Inc 
Barcccclays 
AAAAA 
Testtttt 
Tesco Plc 

我的输出应该如下：

CompanyName 
Barcccclays 
AAAAA 
Testtttt 

提前感谢！

Answer 1

是的，它是可能的，但我不会做它在SQL Server中没有正则表达式的功能：

CREATE TABLE tabC(CompanyName VARCHAR(100)); 

INSERT INTO tabC(CompanyName) 
    SELECT 'HSBC Inc' UNION ALL 
    SELECT 'Barcccclays' UNION ALL 
    SELECT 'AAAAA' UNION ALL 
    SELECT 'Testtttt' UNION ALL 
    SELECT 'Tesco Plc'; 

WITH mul AS 
(
    SELECT REPLICATE(CHAR(32 + N), 4) AS val 
    FROM (select top 95 row_number() over(order by t1.number) as N 
     from master..spt_values t1) AS s 
) 
SELECT * 
FROM tabC c 
WHERE LEN(CompanyName) > 4 
    AND EXISTS (SELECT 1 
       FROM mul 
       WHERE CHARINDEX(mul.val,c.CompanyName) > 0) 

RextesterDemo

它是如何工作的：

1）产生这样的复制值'aaaa'，'bbbb'，'cccc'等

2）检查你的字符串是否包含它。

警告！只有

该解决方案检查ASCII字符从32到126

编辑：

How can incorporate above code like this: select @flag = 1 from tabc where 1 = (WITH mul AS (SELECT REPLICATE(CHAR(32 + N), 4) AS val FROM (select top 95 row_number() over(order by t1.number) as N from master..spt_values t1) AS s) SELECT * FROM tabC c WHERE LEN(CompanyName) > 4 AND EXISTS (SELECT 1 FROM mul WHERE CHARINDEX(mul.val,c.CompanyName) > 0)).

I'm getting this error:If this statement is a common table expression, or a change tracking context clause, the previous statement must be terminated with a semicolon. pls help

如果你需要使用它在上下文中，你不能用它CTE更改为子查询。

SELECT * 
FROM tabC c 
WHERE LEN(CompanyName) > 4 
    AND EXISTS (SELECT 1 
       FROM (SELECT REPLICATE(CHAR(32 + N), 4) AS val 
        FROM (select top 95 row_number() over(order by t1.number) as N 
          from master..spt_values t1) AS s) mul 
       WHERE CHARINDEX(mul.val,c.CompanyName) > 0) 

Answer 2

我会说最简单的解决方案是启用SQL CLR并实施您的条件为user-defined function in .NET。在那里你可以使用正则表达式的能力（例如：Regex类）。

您需要的正则表达式应该是沿着(.)\1{3}的行，它匹配任何字符后面跟着相同的字符至少3次。

例如，UDF可以用C＃编写这样的：

using Microsoft.SqlServer.Server; 
using System; 
using System.Data.SqlTypes; 
using System.Text.RegularExpressions; 

public partial class UserDefinedFunctions 
{ 
    [SqlFunction(DataAccess = DataAccessKind.None, IsDeterministic = true, IsPrecise = true)] 
    public static SqlBoolean ContainsRepeatingCharacters(SqlString input) 
    { 
     const String pattern = @"(.)\1{3}";  
     Boolean hasMatch = Regex.IsMatch(input.ToString(), pattern); 
     return new SqlBoolean(hasMatch); 
    } 
} 

然后，您可以使用它像任何其他UDF：

select companyName 
from companies 
where dbo.ContainsRepeatingCharacters(companyName) = 1 

实现纯TSQL相同的条件下尽一切可能，只是它可能是一个混乱的阅读和维护。例如，考虑this post中的蛮力解决方案，并考虑在未来需要更改所需条件时会发生什么，甚至会更复杂一点。

Answer 3

如果您有一份NGrams8K方便，这是小菜一碟。下面的两种解决方案都很简单，不需要CLR集成，并且在性能方面会打破任何正则表达式的选择。

-- sample data 
DECLARE @table table 
(
    CompanyName varchar(100) 
    unique /* included to simulate an index on this column */ 
); 
INSERT @table values('HSBC Inc'),('Barcccclays'),('AAAAA'),('Testtttt'),('Tesco Plc'); 

-- solution #1 
SELECT companyname 
FROM @table 
CROSS APPLY dbo.ngrams8K(CompanyName,1) 
WHERE charindex(replicate(token,4), CompanyName) > 0 
GROUP BY CompanyName; 

-- solution #2 (if you want to return a boolean) 
SELECT companyname, has4ConsecChars = max(sign(charindex(replicate(token,4), CompanyName))) 
FROM @table 
CROSS APPLY dbo.ngrams8K(CompanyName,1) 
GROUP BY CompanyName; 

结果

companyname 
--------------- 
AAAAA 
Barcccclays 
Testtttt 

companyname  has4ConsecChars 
--------------- --------------- 
AAAAA   1 
Barcccclays  1 
HSBC Inc  0 
Tesco Plc  0 
Testtttt  1