Sams Teach Yourself SQL in 21 Days, Fourth Edition

Optimizing Data Loads by Dropping Indexes

One way to expedite batch updates is by dropping indexes. Imagine the history table with many thousands of rows. That history table is also likely to have one or more indexes. When you think of an index, you normally think of faster table access, but in the case of batch loads, you can benefit by dropping the index(es) (see Day 15).

When you load data into a table with an index, you can usually expect a great deal of index use, especially if you are updating a high percentage of rows in the table. Look at it this way: If you are studying a book and highlighting key points for future reference, you may find it quicker to browse through the book from beginning to end rather than using the index to locate ...