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Why are there so many duplicate indexes in SQL Server?
SQL Server has no safeguards against indexes that duplicate behavior, and therefore a table could conceivably have any number of duplicate or overlapping indexes on it without your ever knowing they were there! This would constitute an unnecessary drain on resources that could easily be avoided.
What happens when you add an index to a table?
Each index that is added to a table will increase the speed of reads that are now able to utilize that index, but at the cost of speed whenever that index needs to be updated. In addition, your index maintenance processes (rebuilding/reorganizing) will now have an additional index to operate on.
How are indexes used to speed up queries?
Effective indexing is the key to keeping your queries running quickly while consuming as few resources as possible in the process. Each index that is added to a table will increase the speed of reads that are now able to utilize that index, but at the cost of speed whenever that index needs to be updated.
How to detect duplicate or overlapping indexes in Excel?
To detect both duplicate indexes AND overlapping indexes, we can modify the query we wrote earlier by using some string manipulation: Only two adjustments were needed to change our query to look for similar data, rather than identical data. First, we removed the equality check on the included columns list.
How are unique indexes created in SQL Server?
A unique constraint also guarantees that no duplicate values can be inserted into the column (s) on which the constraint is created. When a unique constraint is created a corresponding unique index is automatically created on the column (s).
How to identify duplicate columns in SQL Server?
All we have to do is join on table name and compare the columnlist column from the first result set with the substring of the columnlist column from the second result set using the length of the first columnlist column. Of course we will omit exact matches except where the index name is also different. Here is the T-SQL for this query.
What’s the difference between unique index and unique constraint?
A unique index ensures that the values in the index key columns are unique. A unique constraint also guarantees that no duplicate values can be inserted into the column(s) on which the constraint is created.