André Krijnen

Tag: sql 2000

Timestamp and validation

by on Jul.13, 2009, under Programming, sql server, SSIS

Timestamp in SQL Server:

1) The SQL Server timestamp data type has nothing to do with times or dates. SQL Server timestamps are binary numbers that indicate the relative sequence in which data modifications took place in a database. The timestamp data type was originally implemented to support the SQL Server recovery algorithms.

2) It further states Never use timestamp columns in keys, especially primary keys, because the timestamp value changes every time the row is modified.

For a customer we made some changes. And the situation is as follows. We exported the data to excel. Multiple tabels are exported. We changed the data in the excel file and the customer validated the data. We also did export the timetamp with the data. Why? Because we had to import it again to the database. If a Timestamp changed, we should not update the data from the excel file. That’s why.

Problem situation:

Because a timestamp isn’t a varchar, or numeric value, but a binary(8) value we had to convert it. Because we import the data by SSIS back into the database. But the data we imported is from a flat text file. So every column was read as a DT_STR by SSIS, and timestamp in the stored procedure was a datatype of Timestamp. So we did a comparison of a varchar against a timestamp. Well that situation didn’t work out that well.

So what we did was to change the parameter of the stored procedure to varchar. Well SQL Server can’t handle a comparison of varchar against timestamp inside the stored procedure. Of course, so we did try it to convert it to a varbinary(8) or binary(8) and then validate it against the timestamp. Well that didn’t work out that well.

declare @timestamp varbinary(8)
set @timestamp = CONVERT(varbinary(8), '0x0000000001F4AD88')
print @timestamp

returned: 0x3078303030303030

declare @timestamp varbinary(8)
set @timestamp = CONVERT(varbinary(8), 0x0000000001F4AD88)

print @timestamp

returned: 0x0000000001F4AD88

That comparison didn’t work well. So I had to figure an other way to validate on timestamp. When I almost lost my hope I wrote a function in SQL Server.

create function [dbo].[sp_hexadecimal] ( @var varbinary(255) )
returns varchar(255)

      declare @charval varchar(255)
      declare @i int
      declare @length int
      declare @hex char(16)

      select @charval = '0x'
      select @i = 1
      select @length = datalength(@var)
      select @hex = '0123456789abcdef'

      while (@i <= @length)
            declare @tempint int
            declare @firstint int
            declare @secondint int

            select @tempint = convert(int, substring(@var,@i,1))
            select @firstint = floor(@tempint/16)
            select @secondint = @tempint - (@firstint*16)
            select @charval = @charval +
            substring(@hex, @firstint+1, 1) +
            substring(@hex, @secondint+1, 1)

            select @i = @i + 1

return ( @charval )

So what I did was the other. I managed to validate the data on the other way.

it did the trick...

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SQL Server DB Log File truncating…

by on Jan.31, 2008, under maintenance, sql server

Well alot of database administrators forget to truncate their database daily before backing the database up. Well I don’t understand why they are forgetting it. Because it’s a simple procedure you can add before you backup the database. Today I received a database of 5 gigabytes and with a log file of yes you don’t how of 21 gigabytes. So I was using the standard features of SQL Server 2000, but this tool does not his work with the normal truncating options of the database.

After a good search I found out it isn’t that much fun to truncate the database with a procedure. After a search on google it was easy to find the simplest script for database maintenance. I used this script and it really did work. Below you can find out yourself:

  4. DECLARE @LogicalFileName sysname, @MaxMinutes INT, @NewSize INT
  8. *** USE [DATABASE] — This is the name of the database — for which the log will be shrunk.
  9. SELECT @LogicalFileName = 'LOGFILENAME', — Use sp_helpfile to identify the logical file — name that you want to shrink.
  10. @MaxMinutes = 10, — Limit on time allowed to wrap log.
  11. @NewSize = 10 — in MB — Setup / initialize
  12. DECLARE @OriginalSize INT
  14. SELECT @OriginalSize = SIZE — in 8K pages FROM sysfiles WHERE name = @LogicalFileName
  16. SELECT 'Original Size of ' + DB_NAME() + ' LOG is ' + CONVERT(VARCHAR(30),@OriginalSize) + ' 8K pages or ' + CONVERT(VARCHAR(30),(@OriginalSize*8/1024)) + 'MB' FROM sysfiles WHERE name = @LogicalFileName
  18. CREATE TABLE DummyTrans (DummyColumn CHAR (8000) not null) — Wrap log and truncate it.
  20. DECLARE @Counter INT, @StartTime DATETIME, @TruncLog VARCHAR(255)
  22. SELECT @StartTime = GETDATE(), @TruncLog = 'BACKUP LOG ['+ DB_NAME() + '] WITH TRUNCATE_ONLY' — Try an initial shrink.
  24. DBCC SHRINKFILE (@LogicalFileName, @NewSize) EXEC (@TruncLog) — Wrap the log if necessary.
  26. WHILE @MaxMinutes > DATEDIFF (mi, @StartTime, GETDATE()) — time has not expired
  27. AND @OriginalSize = (SELECT SIZE FROM sysfiles WHERE name = @LogicalFileName) — the log has not shrunk
  28. AND (@OriginalSize * 8 /1024) > @NewSize — The value passed in for new size is smaller than the current size.
  30. BEGIN — Outer loop.
  32. SELECT @Counter = 0 WHILE ((@Counter > @OriginalSize / 16) AND (@Counter > 50000))
  33. BEGIN — update
  34. INSERT DummyTrans VALUES ('Fill Log') — Because it is a char field it inserts 8000 bytes.
  35. DELETE DummyTrans SELECT @Counter = @Counter + 1 END — update
  36. EXEC (@TruncLog) — See if a trunc of the log shrinks it.
  37. END — outer loop
  38. SELECT 'Final Size of ' + DB_NAME() + ' LOG is ' + CONVERT(VARCHAR(30),SIZE) + ' 8K pages or ' + CONVERT(VARCHAR(30),(SIZE*8/1024)) + 'MB' FROM sysfiles WHERE name = @LogicalFileName
  39. DROP TABLE DummyTrans PRINT '*** Perform a full database backup ***'

Voila, fill in the database name and the logfile name and you’re done. Run the script within query analyser or other usefull tool. I used this script with SQL Server 2000 and SQL Server 2005. This script can also be used with SQL Server 7. So with the major databases of Microsoft you can use this script. Have fun!!

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