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ankurgupta26
Starting Member
32 Posts |
 Posted - 2002-10-11 : 13:44:52
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| I have read when a select statement is issued SQL serevr loads the data pages in memory from disk. So that when some other user runs the same query sql server will get the data directly from memory instead of getting data from disk to avoid input/Output operation as it's a resource intensive operation.more or less same is applied for an update. only thing before making the changes permanent sql server first writes the data to log cache (write ahead log) and then to buffer cache. The lazy writter process which runs in background checks for the dirty pages and makes them permanent on the disk.Just wondering if delete <tablename> would also work the same wayand also truncate. As we all know truncate statements can also be rolled back in sql server.1) Let me know if my understanding is correct.2) Your comments appreciated on how does a delete & truncate work behind the scenes.Thanks !AnkuR. |
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robvolk
Most Valuable Yak
15732 Posts |
Posted - 2002-10-11 : 14:30:36
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| Books Online describes how TRUNCATE TABLE works in some detail, at least in describing the differences from a DELETE operation. Other than that I don't know how useful it is to know the nuts and bolts of the physical operation. I think if any resource would have more information it would be Inside SQL Server by Microsoft Press. It's a very good book to have if you want to know the real nitty-gritty about SQL Server. |
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Delete statement - Behind the scenes