Some hand-matching of internal/external records may be needed even in an automated reconciliation. The matches will be stored in a database. Rules on matching can be enforced in the application, but there are often good reasons to place them in the database. In Sql Server, a filtered index (with a WHERE clause, in this case excluding Nulls) on the table can make this easier and more correct. Continue reading Simplify Reconciliation Code with Filtered Indexes
Indexes often double as constraints. Each combination of values must only appear once among the columns of an index defined as UNIQUE. The “filtered” index allows some refinement. Suppose that in one column you won’t allow a specific value to appear more than once, but you don’t mind other values being duplicated.
A good example would be the IS_LATEST_VERSION column in a data warehouse table. Continue reading Sql Server Filtered Index as a Unique Constraint on a Specific Value