LOG() function in MySQL is used to calculate the natural logarithm of a specific number. The number must be >0 Otherwise it will return NULL. Syntax :

LOG(X)

Parameter : This method accepts one parameter as mentioned above and described below :

• X : A number whose logarithm value we want to calculate. It should be positive number.

Returns : It returns the natural logarithm of given number x. Example-1 : Logarithm of given number using LOG() function.

SELECT LOG(5) AS Log_Val ;

Output :

Log_Val
1.6094379124341003

Example-2 : Logarithm of 0 using LOG() function.

SELECT LOG(0) AS Log_Val ;

Output :

Log_Val
NULL

Example-3 : The LOG function can also be used to find the logarithmic value of a column data columns. To demonstrate create a table named. Product :

CREATE TABLE Product(
    Product_id INT AUTO_INCREMENT, 
    Product_name VARCHAR(100) NOT NULL,
    Buying_price DECIMAL(13, 2) NOT NULL,
    Selling_price DECIMAL(13, 2) NOT NULL,
    Service_grade Decimal(6, 2) NOT NULL,
    PRIMARY KEY(Product_id)
);

Now inserting some data to the Product table :

INSERT INTO 
    Product(Product_name, Buying_price, Selling_price, Service_grade)
VALUES
    ('Touring Bike', 2019.00, 3009.6, 0.89 ),
    ('Mountain Bike', 3019.50, 4000.56, 1.00 ),
    ('Road Bike', 1019.20, 2000.56, -0.89 ),
    ('Road Bicycle', 1019.50, 1500.56, -1.50 ),
    ('Racing Bicycle', 3019.50, 4000.56, 2.00) ;

So, Our table looks like :

mysql> Select * from Product;
+------------+----------------+--------------+---------------+---------------+
| Product_id | Product_name   | Buying_price | Selling_price | Service_grade |
+------------+----------------+--------------+---------------+---------------+
|          1 | Touring Bike   |      2019.00 |       3009.60 |          0.89 |
|          2 | Mountain Bike  |      3019.50 |       4000.56 |          1.00 |
|          3 | Road Bike      |      1019.20 |       2000.56 |         -0.89 |
|          4 | Road Bicycle   |      1019.50 |       1500.56 |         -1.50 |
|          5 | Racing Bicycle |      3019.50 |       4000.56 |          2.00 |
+------------+----------------+--------------+---------------+---------------+
5 rows in set (0.00 sec)

Now, we are going to find the logarithmic values for all the records present in the Service_grade column.

Select Product_id,  
 Product_name,  
 Buying_price,  
 Selling_price,  
 Service_grade,
 LOG(Service_grade) AS GRADELOG  
 FROM Product;

Output :

+------------+----------------+--------------+---------------+---------------+----------------------+
| Product_id | Product_name   | Buying_price | Selling_price | Service_grade | GRADELOG             |
+------------+----------------+--------------+---------------+---------------+----------------------+
|          1 | Touring Bike   |      2019.00 |       3009.60 |          0.89 | -0.11653381625595151 |
|          2 | Mountain Bike  |      3019.50 |       4000.56 |          1.00 |                    0 |
|          3 | Road Bike      |      1019.20 |       2000.56 |         -0.89 |                 NULL |
|          4 | Road Bicycle   |      1019.50 |       1500.56 |         -1.50 |                 NULL |
|          5 | Racing Bicycle |      3019.50 |       4000.56 |          2.00 |   0.6931471805599453 |
+------------+----------------+--------------+---------------+---------------+----------------------+