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Converting varbinary to numeric type in tsql -- decimal in c# Expand / Collapse
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Posted Thursday, June 27, 2013 8:39 AM
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We are currently dealing with a legacy application, where the decimal numbers from c# are stored in the database (sqlserver) as varbinary types. This (I think) was done to keep formatting with the number.

The problem now is that we can not search/index on the number in the database. It has to be restored to a c# decimal in the application and then only does this make sense.

How can I convert the varbinary to a decimal/numeric type in the sqlserver?

I don't mind creating a new column/table to store the numeric value and formatting information derived from the varbinary.

I know in c# you can create a decimal number by giving it an array of ints.

Here is the description of how c# interprets and converts an int array to decimal type. http://msdn.microsoft.com/en-us/library/aa326746(v=vs.71).aspx

The binary representation of a Decimal number consists of a 1-bit sign, a 96-bit integer number, and a scaling factor used to divide the integer number and specify what portion of it is a decimal fraction. The scaling factor is implicitly the number 10, raised to an exponent ranging from 0 to 28. bits is a four-element long array of 32-bit signed integers. bits [0], bits 1, and bits [2] contain the low, middle, and high 32 bits of the 96-bit integer number. bits [3] contains the scale factor and sign, and consists of following parts: Bits 0 to 15, the lower word, are unused and must be zero. Bits 16 to 23 must contain an exponent between 0 and 28, that indicates the power of 10 to divide the integer number. Bits 24 to 30 are unused and must be zero. Bit 31 contains the sign; 0 meaning positive, and 1 meaning negative. A numeric value might have several possible binary representations; all are equally valid and numerically equivalent. Note that the bit representation differentiates between negative and positive zero. These values are treated as being equal in all operations.

Help is highly appreciated.
Post #1468195
Posted Thursday, June 27, 2013 8:50 AM


SSChampion

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i'm not sure if this will help, I'd really like to see a handful of sample data rows, and their expected values to really be sure.
but can you convert them directly to a decimal and back? or is there more to it than that?

select convert(varbinary,8789961.4513)
select convert(decimal(19,4),0x0B04000131AD397714000000)



Lowell

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Actually, Common Sense is so rare, it should be considered a Superpower. --my son
Post #1468205
Posted Thursday, June 27, 2013 9:32 AM
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If it was simple convertion/cast it would not be a problem.

Here is some sample data.
Name DecimalValue NumericValue
-----------------------------------------------------------------------------
Number2_4 0x14E20100000000000000000000000200 1234.12
Number1 0xCF040000000000000000000000000100 123.1
Number5 0xD9299549000000000000000000000500 12345.12345
Number4 0xF24FBC00000000000000000000000400 1234.1234
Post #1468228
Posted Thursday, June 27, 2013 9:41 AM


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yeah i see that now;
a simple test harness for others to use:
;With MySampleData([Name],[DecimalValue],[NumericValue])
AS
(
SELECT 'Number2_4', 0x14E20100000000000000000000000200, 1234.12 UNION ALL
SELECT 'Number1', 0xCF040000000000000000000000000100, 123.1 UNION ALL
SELECT 'Number5', 0xD9299549000000000000000000000500, 12345.12345 UNION ALL
SELECT 'Number4', 0xF24FBC00000000000000000000000400, 1234.1234
)
SELECT * FROM MySampleData



Lowell

--There is no spoon, and there's no default ORDER BY in sql server either.
Actually, Common Sense is so rare, it should be considered a Superpower. --my son
Post #1468234
Posted Thursday, June 27, 2013 9:43 AM


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Can you post the c# code that does the conversion?

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Post #1468235
Posted Thursday, June 27, 2013 9:54 AM
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Here is the c# code for converting to and from the bytes


byte[] GetBytes ( decimal? value )
{
if ( value == null )
{
return null;
}
byte[] bytes = new byte[16];
int[] bits = Decimal.GetBits ( (decimal) value );
Array.Copy ( BitConverter.GetBytes ( bits[0] ), 0, bytes, 0, 4 );
Array.Copy ( BitConverter.GetBytes ( bits[1] ), 0, bytes, 4, 4 );
Array.Copy ( BitConverter.GetBytes ( bits[2] ), 0, bytes, 8, 4 );
Array.Copy ( BitConverter.GetBytes ( bits[3] ), 0, bytes, 12, 4 );
return bytes;
}
//--------------------
decimal? ToDecimal ( byte[] value )
{
if ( value == null )
{
return null;
}
int[] bits = { BitConverter.ToInt32 ( value, 0 ), BitConverter.ToInt32 ( value, 4 ), BitConverter.ToInt32 ( value, 8 ), BitConverter.ToInt32 ( value, 12 ) };
return new decimal ( bits );
}
Post #1468242
Posted Thursday, June 27, 2013 12:37 PM
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This issue is fully resolved by Lamprey! on sqlteam forum. See answer by visiting

http://www.sqlteam.com/forums/topic.asp?TOPIC_ID=186457
Post #1468294
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