Boolean Expressions in SQL

Boolean expressions are that expression that returns boolean datatype as result. In SQL there are three values for boolean datatype, those are:

TRUE
FALSE
UNKNOWN

The boolean data type can not be specified during table creation, unlike other data types. Boolean expressions are mainly used with WHERE clauses to filter the data from a table. It can include comparison operators and other operators like ‘AND’ operator, ‘OR’ operator, etc.

For a demonstration of boolean expressions, follow the below steps:

Step 1: Create a database

we can use the following command to create a database called geeks.

Query:

CREATE DATABASE geeks;

Step 2: Use database

Use the below SQL statement to switch the database context to geeks:

Query:

USE geeks;

Step 3: Table definition

We have the following demo_table in our geek’s database.

Query:

CREATE TABLE demo_table(
NAME VARCHAR(20),
AGE INT,
CITY VARCHAR(20) );

Step 4: Insert data into a table

Query:

INSERT INTO demo_table VALUES
('ROMY', 22, 'NEW DELHI'),
('PUSHKAR',23, 'NEW DELHI'),
('AKANKSHA',22, 'PUNJAB'),
('SUJATA', 30,'PATNA'),
('PREETI', 26,'BANGLORE'),
('PREM',31,'PUNE'),
('RAM', 34,'PUNE'),
('SHEETAL',32, 'RAJASTHAN'),
('SAMITA',25,'HIMACHAL');

Step 5: View data of the table

Query:

SELECT * FROM demo_table;

Output:

Step 6: Boolean expressions

Example 1: Boolean expression including equal to(=) comparison operator

Query:

SELECT * FROM demo_table
WHERE AGE = 22;                                
{Boolean expression - > (AGE =22)}

This query will return the values from the table where the AGE column has data equal to 22.

Output:

Example 2: Boolean expression including greater than(>) comparison operator

Query :

SELECT * FROM demo_table
WHERE AGE > 22;                                      
{Boolean expression - > (AGE > 22)}

Output:

Example 3: Boolean expression including ‘OR’ operator

OR operator return value when any one of the specified conditions is True.

Query:

SELECT * FROM demo_table
WHERE AGE = 22 OR AGE = 23;         
{Boolean expression - > (AGE = 22 OR AGE = 23)}

Output:

Article Tags :

SQL

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