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# SQL CREATE INDEX Statement * * * The CREATE INDEX statement is used to create indexes in tables. Indexes allow the database application to find data fast; without reading the whole table. * * * ## Indexes An index can be created in a table to find the data more quickly and efficiently. The users cannot see the indexes, they are just used to speed up searches/queries. **Note:** Updating a table with indexes takes more time than updating a table without (because the indexes also need an update). So, it is best to create indexes only on columns (and tables) that will be frequently searched against. ### SQL CREATE INDEX Syntax Creates an index on a table. Duplicate values are allowed: CREATE INDEX index_name ON table_name (column_name) ### SQL CREATE UNIQUE INDEX Syntax Creates a unique index on a table. Duplicate values are not allowed: A unique index means that two rows cannot have the same index value. Creates a unique index on a table. Duplicate values are not allowed: CREATE UNIQUE INDEX index_name ON table_name (column_name) **Note:** The syntax for creating indexes varies amongst different databases. Therefore: Check the syntax for creating indexes in your database. * * * ## CREATE INDEX Examples The following SQL statement creates an index named "PIndex" on the "LastName" column in the "Persons" table: CREATE INDEX PIndex ON Persons (LastName) If you want to create an index on more than one column, you can list the column names within the parentheses, separated by commas: CREATE INDEX PIndex ON Persons (LastName, FirstName)