Indexes are very useful to improve search queries on database tables. For example you are searching for particular record in a database table having millions of records. You will find that search queries taking very less time on tables having indexes enables.
This will creates index on mysql table. This will allow duplicate values also.
CREATE INDEX index_name ON table_name (COLUMN_NAME1, COLUMN_NAME2, ...)
CREATE UNIQUE INDEX:-
This will creates index on mysql table. With uses of UNIQUE keyword this will not allow duplicate values.
CREATE UNIQUE INDEX index_name ON table_name (COLUMN_NAME1, COLUMN_NAME2, ...)
1. CREATE INDEX Examples:-
For this example I have a table named Users with thousands of records in mysql database. The table structure is as following in screenshot.
Now use following command to create index named Users_Idx1 on table Users based on column username.
mysql>CREATE INDEX Users_Idx1ON Users (username);
Use UNIQUE keyword with the query to create index with unique records.
mysql>CREATE UNIQUE INDEX Users_Idx1ON Users (username);
2. SHOW INDEX Examples:-
Use following sql command to list all indexes for a mysql table. The below query will delete Users_Idx1 index from Users table in current database.
mysql>SHOW INDEX FROM Users;
3. DELETE INDEX Examples:-
Use following sql command to delete index on mysql table.
mysql>ALTER TABLE Users DROP INDEX Users_Idx1 ;