Data comparison without unique key

We are importing data from external source. This data does not have a global key, so we have Varchars, Dates, etc. to match.

The question i开发者_JS百科s: How to make the perfomance of Varchar comparison better? Also, it there any tool that can allow to see match percentage (Like similiarity of rows: 90%)

Thanks!

Whilst not a direct answer to your question, if you're importing data then Integration Services (if you're not already using it) would be a decent choice. A couple of the transformations included in SSIS allow for 'fuzzy matching' - that is, matching data based on a confidence level of similarity.

For finding "similar" matches you could use a sounds like comparison:

WHERE SOUNDEX(some_column) = SOUNDEX(‘some_string’)

Are you looking for a tool to compare data? http://www.red-gate.com/products/sql-development/sql-data-compare/