LEFT Function - SQL

Overview

The LEFT function in SQL returns the specified number of characters from the beginning of a string. It is useful for extracting a portion of a string from the left side.

Example:

SELECT LEFT('Astronomy', 5)

Syntax:

SELECT LEFT(string, num_of_characters)

string is the string from which you want to extract characters.

num_of_characters is the number of characters to extract from the beginning of the string.

Sample Data:

    
            department_id
            first_name
        
            3
            Frank
        
            2
            Jane
        
            3
            Ashley
        
            NULL
            Glenn
        
            2
            Kelly
        
            1
            Richard
        
            1
            George
        
            5
            Kyle
        
            2
            James
        
            1
            Gustavo

department_id	first_name
3	Frank
2	Jane
3	Ashley
NULL	Glenn
2	Kelly
1	Richard
1	George
5	Kyle
2	James
1	Gustavo

Example: Hard-coded value

In this example, we are returning the 5 characters to the left of the string ‘astronomy,’ the final output is ‘astro.’

Example: Query without the WHERE Statement

In this example, we are returning the 3 characters to the left of all of the rows in the first_name column.

Example: Query with the WHERE Statement

In this example, we are returning the 3 characters to the left of all of the rows in the first_name column where the department_id equals 1.