| | Sams Teach Yourself SQL in 24 Hours, Third Edition By Ronald R. Plew, Ryan K. Stephens | | Table of Contents | | | | Hour 16. Using Indexes to Improve Performance |
Q&A | Q1: | Does an index actually take up space the way a table does? | | A1: | Yes. An index takes up physical space in a database. In fact, an index can become much larger than the table for which the index was created. | | Q2: | If you drop an index for a batch job to complete faster, how long does it take to re-create the index? | | A2: | Many factors are involved, such as the size of the index being dropped, CPU usage, and the machine's power. | | Q3: | Should all indexes be unique indexes? | | A3: | No. Unique indexes allow no duplicate values. There may be a need for the allowance of duplicate values in a table. | |
|