Usage and examples of the SQL INDEX keyword

SQL Keyword Reference

CREATE INDEX (Create Index)

The CREATE INDEX command is used to create an index in a table (allowing duplicate values).

Indexes are used to retrieve data from the database very quickly. Users do not see indexes; they are only used to speed up searches/Query.

The following SQL creates an index named 'idx_lastname' on the 'LastName' column of the 'Persons' table:

CREATE INDEX idx_lastname
ON Persons (LastName);

If you want to create an index on a column combination, you can list the column names within parentheses and separate them with commas:

CREATE INDEX idx_pname
ON Persons (LastName, FirstName);

Note:The syntax for creating indexes varies between different databases. Therefore: Check the syntax used to create indexes in the database.

DROP INDEX (Delete Index)

The DROP INDEX command is used to delete an index from a table.

MS Access：

DROP INDEX index_name ON table_name;

SQL Server：

DROP INDEX table_name.index_name;

DB2 / Oracle：

DROP INDEX index_name;

MySQL：

ALTER TABLE DROP INDEX ;

SQL Keyword Reference