Mysql Indexes
by Rekha[ Edit ] 2010-09-23 15:48:50
Mysql Indexes
A database index is a data structure that improves the speed of operations in a table. Indexes can be created using one or more columns, providing the basis for both rapid random lookups and efficient ordering of access to records.
While creating index it should be considered that what are the columns which will be used to make SQL queries and create one or more indexes on those columns.
Practically, Indexes are also type of tables which keeps primary key or index field and a pointer to each record in to the actual table.
The users cannot see the indexes, they are just used to speed up queries and will be used by Database Search Engine to locate records very fast.
INSERT and UPDATE statements takes more time on tables having indexes where as SELECT statements become fast on those tables. The reason is that while doing insert or update, database need to insert or update index values as well.
CREATE UNIQUE INDEX index_name
ON table_name ( column1, column2,...);
