SQL Create Index on Table.

Add a Table Index

• In a relational database management system, an index is a mechanism for boosting performance.
• This is true for the selecting of data from tables, but not for the updates, it may be slow down the performance.
  Syntax:
  MySQL, Oracle, SQL server, PostgreSQL:

  CREATE [UNIQUE] INDEX index_name ON table_name (column_name)

  Example:

  create index CustomerID on Orders (Customer_id)

• We can create a Composite index of two or more columns (fields) when it will provide the best search as a unit because of their logical relationship.

  Example:

  create index Fullname on Customer (First_name, Last_Name);

• A unique index is one in which no two rows are permitted to have the same index value.
• We usually create a unique index on the primary keys columns.
  Example:

  create unique index TitleIndex on bookstore (PUBLISHER);