Range Query In MySQL

Database applications are a common feature in workplaces.

In MySQL, as in any other database system, a range query retrieves data within a certain value range. When you create a range query in MySQL, you specify that the values for certain columns should be within a set range. You can optionally apply a range to more than one column in the data you are retrieving. The results of a range query only contain records with values within the range specified, which is often useful within database applications.

Query

MySQL queries define sets of data within databases. When developing database applications, programmers create one or more queries to facilitate application tasks. A query generally specifies the required data in terms of tables and columns, but can also enforce restrictions. The range query is an example of this, where the values used for one or more columns within the data being retrieved must fall within a certain range. The range query works by first specifying the entire query, then listing the range specifications to be enforced on it, so that MySQL iterates through the records and only returns those with the correct values.

Syntax

One of the main techniques for creating range queries in MySQL is the "where" clause. Using the "where" clause, developers can create queries which specify range conditions for certain columns. The following example syntax demonstrates a range query:

SELECT * FROM some_object WHERE object_size > 10 AND object_size < 20;

This query enforces a range for the "object_size" column within a table named "some_object." The query results will only contain records with values falling between "10" and "20" for the specified column. Note that the query actually contains two range specifications, linked using the "and" keyword.

Operators

Developers use a variety of operators to specify a range within a MySQL query. The "greater than" and "less than" operators are among the most common, as in the "some_table" example. Developers can also choose "greater than or equal to" as follows:

WHERE object_size >= 10

Other operators specify that a value must be equal, or not equal, to another value, or that a value must not be null. Range operators and clauses can be combined using the "and" and "or" keywords to chain multiple specifications together.

Uses

Range queries are often useful in MySQL database applications. For example, in a database which stores records of people including their dates of birth, it could be useful to query those records for people who are above or below a certain age. Specifying a range query is more efficient than simply pulling all of the records from a table, then processing them within the application to check which ones are within the desired range. The range facility is an aspect of MySQL which is designed to allow tailored data management within applications.

References

• MySQL Documentation: Range Optimization
• Tizag: MySQL Tutorial - Where
• W3Schools: SQL WHERE Clause
• W3Schools: SQL AND & OR Operators

Resources

• PHP Manual: mysql_query
• W3Schools: SQL SELECT Statement
• MySQL Documentation: SELECT Syntax
• MySQL Documentation: WHERE Clause Optimization