How do you convert VARCHAR to TIMESTAMP in MSSQL?

Question

You\'d like to call a stored proc on MS SQL that has a parameter type of TIMESTAMP within T-SQL, not ADO.NET using a VARCHAR value (e.g. \'0x0000000002C490C8\').

Wha

Answer 1

A timestamp datatype is managed by SQL Server. I've never seen it used anywhere other than as a table column type. In that capacity, the column of type timestamp will give you a rigorous ordinal of the last insert/update on the row in relation to all other updates in the database. To see the most recent ordinal across the entire database, you can retrieve the value of @@DBTS or rowversion().

Per http://msdn.microsoft.com/en-us/library/ms182776(SQL.90).aspx

timestamp (Transact-SQL)

is a data type that exposes automatically generated, unique binary numbers within a database. timestamp is generally used as a mechanism for version-stamping table rows. The storage size is 8 bytes. The timestamp data type is just an incrementing number and does not preserve a date or a time. To record a date or time, use a datetime data type.

Hence, the volatile value of a timestamp column cannot be set and is subject to change upon any modifaction to the row. You can, however, freeze the timestamp value to a varbinary(8) value.

For example, say you had a source table and a target table.

CREATE TABLE tblSource (
Id int not null
colData int not null
colTimestamp timestamp null)

CREATE TABLE tblTarget (
Id int not null
colData int not null
colTimestampVarBinary varbinary(8) null)

Then, in an extraction process, you might want to capture everything that has been updated since the last time you ran the extraction process.

DECLARE @maxFrozenTargetTimestamp varchar(8)
SELECT @maxFrozenTargetTimestamp = max(colStamp) FROM tblTarget

INSERT tblTarget(Id, colData, colTimestampVarBinary)
SELECT 
Id
,colData
colTimestampVarBinary = convert(varbinary(8) colTimestamp)
FROM 
tblSource 
WHERE
tblSource.colTimestamp > @maxFrozenTargetTimestamp

If you are having issues, my first guess would be that crux of your problem is in the conversion of a varchar to a varbinary(8), and not to a timestamp type.

For more info (perhaps too much) , see the comment (fourth one down) I left to the blog post http://vadivel.blogspot.com/2004/10/about-timestamp-datatype-of-sql-server.html?showComment=1213612020000