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MySQL Tutorial

PostgreSQL LEFT() function

LEFT() function

The PostgreSQL left() function is used to extract n number of characters specified in the argument from the left of a given string. When the value of n is negative, the extraction will happen from left except last n characters.

Syntax:

left(string,n) 

PostgreSQL Version: 9.3

Pictorial Presentation of PostgreSQL LEFT() function

Pictorial presentation of PostgreSQL LEFT() function

Example: PostgreSQL LEFT() function:

In the example below, the left function extracted 3 characters from the left of the string 'w3resource'.

Code:

SELECT left('w3resource',3)
AS "Extract 3 characters from the left";

Sample Output:

 Extract 3 characters from the left
------------------------------------
 w3r
(1 row)

Example: PostgreSQL LEFT() function using negative value:

In the example below, the left function extracted all the characters from the left side except 3 rightmost characters from the string 'w3resource', because the value of extracting character number is negative.

Code:

SELECT left('w3resource',-3)
AS "Extract all characters except 3 rightmost";

Sample Output:

 Extract all characters except 3 rightmost
-------------------------------------------
 w3resou
(1 row)

Example: PostgreSQL LEFT() function using columns of table:

Sample Table: employees


If we want to display the first_name, last_name for those employees whose first 3 characters of their name contain 'Nan' from employees table, the following sql statement can be used:

Code:

SELECT first_name, last_name 
FROM employees 
WHERE left(first_name,3)='Nan';

Sample Output:

 first_name | last_name
------------+-----------
 Nancy      | Greenberg
 Nanette    | Cambrault
 Nandita    | Sarchand
(3 rows)

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