Published 16 November 2017
CAST/CONVERT to variable-size types without length
The length of VARCHAR, VARBINARY and NVARCHAR datatype in a CAST or CONVERT clause wasn’t explicitly specified.
When you convert a datatype to a variable-size type, you do not have to specify the size. If you don’t do so, SQL Server will use a variable-size type sufficient to hold the string. It is better to specify the size because SQL Server has no idea what size you may subsequently need.