SQL DROP INDEX Keyword

The SQL DROP INDEX keyword is used to delete a index on a table. Indexes are useful to retrieve data from the database more quickly and speeds up the search queries. Indexes are not visible to the end users. Along with this, updating a table with indexes takes more time as compared to a table without any indexes because indexes are updated. Therefore it is advised to create indexes only on frequently searched columns.

The INSERT and UPDATE statements take more time on tables having indexes, whereas the SELECT statements become fast on those tables. The reason is that while performing insert or update operation, the database update the indexes as well.

SQL DROP INDEX

The SQL DROP INDEX statement is used to delete a index on a table.

Syntax

The syntax for using SQL DROP INDEX statement is given below:

/* MySQL / MS Access / SQL Server */
DROP INDEX index_name ON table_name;

/* MySQL / SQL Server */
ALTER TABLE table_name
DROP INDEX index_name;

/* SQL Server */
DROP INDEX table_name.index_name;

/* Oracle */
DROP INDEX index_name;

SQL DROP INDEX Example

Consider a table called Employee which contains an index named idx_name. To drop this index, the following statement can be used:

/* MySQL / MS Access / SQL Server */
DROP INDEX idx_name ON Employee;

/* MySQL / SQL Server */
ALTER TABLE Employee
DROP INDEX idx_name;

/* SQL Server */
DROP INDEX Employee.idx_name;

/* Oracle */
DROP INDEX idx_name;