SQL CREATE UNIQUE INDEX Keyword
The SQL CREATE UNIQUE INDEX keyword is used to create indexes on a table with unique name. 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 syntax for using SQL INDEX statement is given below:
/* creating unique index_name */ CREATE UNIQUE INDEX index_name ON table_name (column1, column2, ...);
SQL INDEX statement Examples
The below mentioned SQL code creates unique index on column Name of Employee table.
CREATE UNIQUE INDEX idx_name ON Employee (Name);
To create a unique index on multiple columns (Name and EmpID) of a table (Employee), the SQL code is given below:
CREATE UNIQUE INDEX idx_empid ON Employee (Name, EmpID);
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