Are there any benefits to using sql_variant over varchar in SQL Server?

Question

I currently have a database table setup as follows (EAV - business reasons are valid):

• Id - int (PK)
• Key - unique, varchar(15)
• Value - varchar(10

Answer 1

I don't see that it has been mentioned yet, so I'll mention that a fairly common approach to this problem is a table like this:

• Id - int (PK)
• Key - unique, varchar(15)
• ValueType - Integer (0 - String, 1 - Integer, 3 - Float) (optional)
• StringValue - varchar(1000)
• IntValue - Integer
• FloatValue - Double

Advantages:

• Data is saved in its appropriate form (storing ints as strings wastes a lot of bits)
• You can do fancy queries like WHERE left(key,5) = 'SHOES', and IntValue>5
• The ValueType column is only useful you are using prefix/suffixes on your keys (to retrieve sets of keys) and the set could be of mixed type. i.e. WHERE left(key,4) = 'Size' and ValueType = 1

Disadvantages:

• Everywhere where you use this table you have to ensure that you/get/set the correct Value column
• If you decide you need/want the ValueType column, you have to ensure that you get/set it correctly.