How to create an index

       CREATE [UNIQUE] INDEX|KEY indexName ON tableName (columnName1 [ASC|DESC] [, columnName2 [ASC|DESC]]...)
      

      CREATE INDEX customerID ON orders (customerID);
      

      CREATE UNIQUE INDEX emailAddress ON customers (emailAddress);
      

      CREATE UNIQUE INDEX customerIDorderNumber ON orders (customerID, orderNumber);
      

      CREATE INDEX orderTotal ON orders (orderTotal DESC);
      

      CREATE TABLE customers (
        customerID INT NOT NULL AUTO_INCREMENT,
        emailAddress VARCHAR(255) NOT NULL,
        firstName VARCHAR(60)NOT NULL,
        
        PRIMARY KEY (customerID), 
        UNIQUE INDEX emailAddress (emailAddress), 
        INDEX firstName (firstName) 
      );
      

      DROP INDEX firstName ON customers;
      

Description

• An index improves performance when MySQL searches for rows in the table.
• MySQL automatically creates an index for primary keys and for unique constraints.
• You can use the CREATE TABLE statement to create indexes for a table.
• You can use the CREATE INDEX statement to add an index to a table.
• You can use the DROP INDEX statement to drop an index.