MySQL: Declaring Variables

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MySQL: Declaring Variables

2023-03-28 00:48| 来源: 网络整理| 查看: 265

This MySQL tutorial explains how to declare variables in MySQL with syntax and examples.

What is a variable in MySQL?

In MySQL, a variable allows a programmer to store data temporarily during the execution of code.

Syntax

The syntax to declare a variable in MySQL is:

DECLARE variable_name datatype [ DEFAULT initial_value ] Parameters or Arguments variable_name The name to assign to the variable. datatype The datatype to assign to the variable. DEFAULT initial_value Optional. It is the value initially assigned to the variable when it is declared. If an initial_value is not specified, the variable is assigned a value of NULL. Example - Declaring a variable

Below is an example of how to declare a variable in MySQL called vSite.

DECLARE vSite VARCHAR(40);

This example would declare a variable called vSite as a VARCHAR(40) data type.

You can then later set or change the value of the vSite variable, as follows:

SET vSite = 'TechOnTheNet.com';

This SET statement would set the vSite variable to a value of 'TechOnTheNet.com'.

Example - Declaring a variable with an initial value (not a constant)

Below is an example of how to declare a variable in MySQL and give it an initial value. This is different from a constant in that the variable's value can be changed later.

DECLARE vSite VARCHAR(40) DEFAULT 'TechOnTheNet.com';

This would declare a variable called vSite as a VARCHAR(40) data type and assign an initial value of 'TechOnTheNet.com'.

You could later change the value of the vSite variable, as follows:

SET vSite = 'CheckYourMath.com';

This SET statement would change the vSite variable from a value of 'TechOnTheNet.com' to a value of 'CheckYourMath.com'.

NEXT: AUTO_INCREMENT

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MySQL: Declaring Variables

MySQL: Declaring Variables

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