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Home 2016 October MySQL: SELECT with Index Hint option to Optimize the Query

MySQL: SELECT with Index Hint option to Optimize the Query

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The Table Indexes are always the main focus to improve the performance of any SQL Query.
In MySQL, We can provide INDEX Hint to Query Optimizer for choosing our analyzed Index.

In most of the cases, Query Planner and Query Optimizer are accurate to choose perfect Index.
But sometimes, still It is required to give Index Hint for reducing the overall Query Planning Time.

If we know that this Index is good for this query, we should Provide the Hint to Query Optimizer.

Here, You can also access one related article.

MySQL: Script to find Index Usage Statistics of a Database

MySQL supports command like USE INDEX, IGNORE INDEX, FORCE INDEX, which we can use for Index Hint.

The USE INDEX hint tells MySQL to use only one of the named indexes to find rows in the table.
The IGNORE INDEX tells MySQL to not use some particular index or indexes.
The FORCE INDEX hint acts like USE INDEX , with the addition that a table scan is assumed to be very expensive.

Prepared small demonstration on this.

Create a sample table:

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CREATE TABLE tbl_EmployeeDetails
(
EmpID INTEGER PRIMARY KEY
,EmpName VARCHAR(50)
,EmpSalary BIGINT
,DepartmentName VARCHAR(50)
);

Insert few sample Records:

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INSERT INTO tbl_EmployeeDetails
VALUES
(1,'Anvesh',80000,'Sales')
,(2,'Neevan',90000,'Sales')
,(3,'Jenny',50000,'Production')
,(4,'Roy',60000,'Production')
,(5,'Martin',30000,'Research')
,(6,'Mahi',85000,'Research')
,(7,'Kruti',45000,'Research')
,(8,'Manish',75000,'Research');

Create few sample Indexes:

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CREATE INDEX idx_tbl_EmployeeDetails_EmpName ON tbl_EmployeeDetails (EmpName);
CREATE INDEX idx_tbl_EmployeeDetails_DepartmentName ON tbl_EmployeeDetails (DepartmentName);
CREATE INDEX idx_tbl_EmployeeDetails_EmpName_EmpSalary ON tbl_EmployeeDetails (EmpName,EmpSalary);

Using USE INDEX:

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SELECT *FROM tbl_EmployeeDetails
USE INDEX (idx_tbl_EmployeeDetails_EmpName)
WHERE EmpName = 'Roy';
 
SELECT *FROM tbl_EmployeeDetails
USE INDEX (idx_tbl_EmployeeDetails_EmpName_EmpSalary)
WHERE EmpName = 'Roy' AND EmpSalary > 50000;

Using IGNORE INDEX:

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SELECT *FROM tbl_EmployeeDetails
IGNORE INDEX (idx_tbl_EmployeeDetails_EmpName)
WHERE EmpName = 'Roy' AND EmpSalary > 50000;

Using FORCE INDEX:

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SELECT *FROM tbl_EmployeeDetails
FORCE INDEX (idx_tbl_EmployeeDetails_EmpName)
WHERE EmpName = 'Roy' AND EmpSalary > 50000;

Oct 19, 2016Anvesh Patel
MySQL 5.7: Script to find list of Active InnoDB Temp Tables using INNODB_TEMP_TABLE_INFOMySQL: Controlling Query Optimizer to choose the Best Execution Plan
Anvesh Patel
Anvesh Patel

Database Engineer

October 19, 2016 MySQLAnvesh Patel, database, database research and development, dbrnd, FORCE INDEX, IGNORE INDEX, index, Index Hint, index usage, MySQL, MySQL Command, MySQL Database Administrator, MySQL Database Designing, MySQL Database Programming, MySQL Error, MySQL Performance Tunning, MySQL Query, MySQL Tips and Tricks, Query Optimizer, USE INDEX
About Me!

I'm Anvesh Patel, a Database Engineer certified by Oracle and IBM. I'm working as a Database Architect, Database Optimizer, Database Administrator, Database Developer. Providing the best articles and solutions for different problems in the best manner through my blogs is my passion. I have more than six years of experience with various RDBMS products like MSSQL Server, PostgreSQL, MySQL, Greenplum and currently learning and doing research on BIGData and NoSQL technology. -- Hyderabad, India.

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