Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
How to declare a variable in MySQL for a normal query?
You can declare a variable using @anyVariablename which is a session variable. To create a session variable, you need to use SET command.
The syntax is as follows
SET @anyVariableName:=anyValue;
You can declare a local variable using DECLARE command. The syntax is as follows
DECLARE yourVariableName datatype
You can set the default value at the time of creating a variable. The syntax is as follows
DECLARE yourVariableName datatype default ‘yourValue’
Here is the demo of session variable. To understand it, let us create a table.
The query to create a table is as follows
mysql> create table SessionVariableDemo -> ( -> EmployeeId varchar(10), -> EmployeeName varchar(30), -> EmployeeAge int -> ); Query OK, 0 rows affected (0.70 sec)
Insert some records in the table using insert command. The query is as follows
mysql> insert into SessionVariableDemo values('EMP-101','Carol',30);
Query OK, 1 row affected (0.20 sec)
mysql> insert into SessionVariableDemo values('EMP-102','John',26);
Query OK, 1 row affected (0.20 sec)
mysql> insert into SessionVariableDemo values('EMP-103','Bob',25);
Query OK, 1 row affected (0.19 sec)
mysql> insert into SessionVariableDemo values('EMP-104','Sam',32);
Query OK, 1 row affected (0.14 sec)
mysql> insert into SessionVariableDemo values('EMP-105','Mike',35);
Query OK, 1 row affected (0.11 sec)
mysql> insert into SessionVariableDemo values('EMP-106','David',33);
Query OK, 1 row affected (0.15 sec)Display all records from the table using select statement. The query is as follows
mysql> select *from SessionVariableDemo;
The following is the output
+------------+--------------+-------------+ | EmployeeId | EmployeeName | EmployeeAge | +------------+--------------+-------------+ | EMP-101 | Carol | 30 | | EMP-102 | John | 26 | | EMP-103 | Bob | 25 | | EMP-104 | Sam | 32 | | EMP-105 | Mike | 35 | | EMP-106 | David | 33 | +------------+--------------+-------------+ 6 rows in set (0.00 sec)
Now, create a session variable using SET command. After that we will use this variable in the query to get all employee records with age greater than 30.
Let us create a session variable using SET command
mysql> set @AgeGreaterThan30:=30; Query OK, 0 rows affected (0.00 sec)
Here is the query that will use the session variable to get the employee records with age greater than 30
mysql> select *from SessionVariableDemo where EmployeeAge > @AgeGreaterThan30;
The following is the output
+------------+--------------+-------------+ | EmployeeId | EmployeeName | EmployeeAge | +------------+--------------+-------------+ | EMP-104 | Sam | 32 | | EMP-105 | Mike | 35 | | EMP-106 | David | 33 | +------------+--------------+-------------+ 3 rows in set (0.00 sec)
3K+ Views
