在sql server中优化游标查询

-1

我们拥有一个拥有更多10,000,000条记录的数据库。以下语句用于用每个记录中的某些词替换另一个表中的另一个词，但由于有很多记录执行甚至在一整天内都没有完成，因此它是否可以优化？在sql server中优化游标查询

DECLARE My_Cursor CURSOR 
FOR 
    SELECT 
     full_santance 
    , id 
    FROM 
     dbo.combined 
    WHERE 
     id BETWEEN 9000000 AND 10000000 

DECLARE My_Cursor_r CURSOR 
FOR 
    SELECT 
     old 
    , new 
    FROM 
     dbo.changesTable 

DECLARE @full_santance varchar(500) 
DECLARE @id numeric(18, 0) 
DECLARE @word_old varchar(500) 
DECLARE @word_new varchar(500) 
DECLARE @corrected varchar(500) 
DECLARE @r_word varchar(500) 

OPEN My_Cursor 
FETCH NEXT FROM My_Cursor INTO @full_santance, @id 
WHILE @@FETCH_STATUS = 0 
     BEGIN 
      SET @corrected = @full_santance 

      OPEN My_Cursor_r 
      FETCH NEXT FROM My_Cursor_r INTO @word_old, @word_new 
      WHILE @@FETCH_STATUS = 0 
        BEGIN 
         IF @corrected LIKE '%[^a-z]' + REPLACE(RTRIM(@word_old),'_', '') + '[^a-z]%' 
          OR @corrected LIKE '%[^a-z]' + REPLACE(RTRIM(@word_old), '_', '') 
          OR @corrected LIKE REPLACE(RTRIM(@word_old), '_','') + '[^a-z]%' 
          OR @corrected LIKE REPLACE(RTRIM(@word_old), '_','') 
          BEGIN 
           SET @corrected = REPLACE(@corrected,REPLACE(RTRIM(@word_old),'_', ' '),REPLACE(RTRIM(@word_new),'_', ' ')) 
          END 

         FETCH NEXT FROM My_Cursor_r INTO @word_old, @word_new 
        END 

      CLOSE My_Cursor_r 

      IF @corrected <> @full_santance 
       BEGIN 
        UPDATE 
         dbo.combined 
        SET 
         full_santance = @corrected 
        WHERE 
         id = @id 
       END 

      FETCH NEXT FROM My_Cursor INTO @word, @id 
     END 
CLOSE My_Cursor 
DEALLOCATE My_Cursor 
DEALLOCATE My_Cursor_r

来源

2014-02-24 user1097275

同时显示表和表列的小样本数据需要由其中一个和两个表的关系进行更新。 – KumarHarsh

我的猜测是内层游标可能很容易重写而没有游标。另外 - 这是一个定期运行或是一次性更新？因为如果它是一次性的，我会正确地尝试在另一个表/数据库中执行此操作，然后一次更新所有行。（10.000.000条记录可能听起来很多，但它不应该是）。如果它经常运行，那为什么？ –

DECLARE @combined TABLE (id int, full_santance varchar(max)) 
INSERT @combined VALUES 
(1, 'the quick brown fox jumped over the lazy dog'), 
(2, 'the dog days of summer') 

DECLARE @changesTable TABLE (old varchar(max), new varchar(max)) 
INSERT @changesTable VALUES 
('dog','cat'), 
('the','a') 

SELECT 
    id, 
    LTRIM((
    SELECT ' '+ISNULL(new,word) 
    FROM @combined c2 
    CROSS APPLY (SELECT CAST('<a>'+REPLACE(full_santance,' ','</a><a>')+'</a>' AS xml) xml1) t1 
    CROSS APPLY (SELECT n.value('.','varchar(max)') AS word FROM xml1.nodes('a') x(n)) t2 
    LEFT JOIN @changesTable ON word = old 
    WHERE c1.id = c2.id 
    FOR XML PATH('') 
)) 
FROM @combined c1

来源

2014-02-24 15:13:40 Anon

这正是我所需要的，非常感谢 – user1097275

在sql server中优化游标查询

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