How the LEFT() Function Works in MySQL

In MySQL, the LEFT() function returns the leftmost characters from a string. The number of characters returned is determined by the second argument.

Syntax

The syntax goes like this:

LEFT(str,len)

Where str is the string that contains the substring you need to return, and len is the number of characters from the left you want returned.

Example 1 – Basic Usage

Here’s an example where I select the first 2 characters from a string:

SELECT LEFT('Forest', 2) AS Result;

Result:

+--------+
| Result |
+--------+
| Fo     |
+--------+

Example 2 – Spaces

The function returns any spaces within the string (and includes them in its calculation). For example, if I add a leading space to the previous example, here’s the result:

SELECT LEFT(' Forest', 2) AS Result;

Result:

+--------+
| Result |
+--------+
|  F     |
+--------+

If this is undesirable, you can always use the TRIM() function to remove the space.

SELECT LEFT(TRIM(' Forest'), 2) AS Result;

Result:

+--------+
| Result |
+--------+
| Fo     |
+--------+

Example 3 – Database Query

Here’s an example of how this function might look within a database query:

USE Music;
SELECT 
    ArtistName AS Original, 
    LEFT(ArtistName, 3) AS Modified
FROM Artists
LIMIT 5;

Result:

+------------------+----------+
| Original         | Modified |
+------------------+----------+
| Iron Maiden      | Iro      |
| AC/DC            | AC/      |
| Allan Holdsworth | All      |
| Buddy Rich       | Bud      |
| Devin Townsend   | Dev      |
+------------------+----------+

In this example, we get the first 3 characters from the ArtistName column and compare it to the original string.

Example 4 – NULL Arguments

The function returns NULL if any of the arguments is NULL. Here’s an example where the first argument is NULL:

SELECT LEFT(NULL, 5) AS Result;

Result:

+--------+
| Result |
+--------+
| NULL   |
+--------+

And here’s an example where the second argument is NULL:

SELECT LEFT('Forest', NULL) AS Result;

Result:

+--------+
| Result |
+--------+
| NULL   |
+--------+