performancestored-proceduresoptimizationsql-server-2008-r2cursors

How to replace cursor inside Stored Procedure for faster Execution in MS SQL?


I have written the below code for splitting string, but it takes a long time to execute. Please help me re-write my code to optimize the query. I have tried hard to find the result, but i didn't get how to apply the logic to replace the cursor.

declare @table as nvarchar(50),@column as nvarchar(max),@delimiter
as nvarchar(1),@tablekey as nvarchar(max)

BEGIN  
SET NOCOUNT ON;  
 set @table='QAT_Tsentences'
 set @column='SentenceElID'
 set @delimiter='|'
 set @tablekey='ID'

 declare @sql as nvarchar(max), @tabkey as nvarchar(max),  @txt as 
 nvarchar(1000), @txtSplitted as nvarchar(255)  
 DECLARE @pos integer--, @delimiter as nchar(1)  
 DECLARE @Leftpiece nvarchar(255), @Rightpiece as nvarchar(255)  


 CREATE TABLE #t(tablekey  nvarchar(max), txt nvarchar(1000))  
 set @sql= 'INSERT #t select '+@tablekey+','+@column+' from '+@table+' where 
 '+@column+' is not null'  

  exec(@sql)  

  drop table QAT_txtsplitted  
  CREATE TABLE QAT_txtsplitted(tablekey  nvarchar(max), txt [nvarchar] 
 (max), txtSplitted [nvarchar](max), ID INT NOT NULL IDENTITY(1,1))  



  DECLARE c1 CURSOR   
  FOR  
   SELECT tablekey, txt  
    FROM #t  

   OPEN c1  

   FETCH NEXT FROM c1  
   INTO @tabkey,@txt  
    While (@@Fetch_status = 0)  
    BEGIN   

    SET @Rightpiece = @txt  
    IF RIGHT(RTRIM(@Rightpiece),1) <> @delimiter  
    SET @Rightpiece = @Rightpiece  + @delimiter  
    SET @pos =  CHARINDEX(@delimiter, @Rightpiece)  

    WHILE @pos <> 0   
    BEGIN  
    SET @Leftpiece = LEFT(@Rightpiece, @pos - 1)  
     INSERT INTO  QAT_txtsplitted (tablekey,txt,txtsplitted) VALUES  
      (@tabkey,@txt, @Leftpiece);  
      SET @Rightpiece = STUFF(@Rightpiece, 1, @pos, '')  
      SET @pos =  CHARINDEX(@delimiter, @Rightpiece)  
       END  
       FETCH NEXT FROM c1  
       INTO @tabkey,@txt  

       END  

  CLOSE c1  
     DEALLOCATE c1  
     drop table #t  
     nchar(1),@tablekey as decimal(15))  
     print 'table results : QAT_txtsplitted'  

     END 

Please find below my result where i have tried to split for a particular tablekey. enter image description here


Solution

  • Here is part of a SP THAT I wrote to remove a cursor

    BEGIN
        DECLARE @Modules TABLE
        (
            ID INT IDENTITY(1,1)
            , ModuleId INT
            , ModuleShortName NVARCHAR(256)
            , ModuleTableName NVARCHAR(260)
        )
    
        INSERT INTO @Modules select ModuleId,ModuleShortName ,ModuleTableName  from Mods
    
        DECLARE @Count INT, @Counter INT, @ModuleId INT, @ModuleTableName NVARCHAR(260)
        SELECT @Count = COUNT(*) FROM @Modules m
        SET @Counter = 1
    
    
    
        WHILE @Counter <= @Count
        BEGIN
            SELECT @ModuleId = ModuleId, @ModuleTableName = ModuleTableName FROM @Modules m WHERE ID = @Counter -- extracting values from the table by counternum
    
             -- do something with data
            -- puttin inner logic
    
    
            SET @Counter = @Counter + 1
        END