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.
create unique index TitleIndex on bookstore (PUBLISHER);
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