MySQL Tutorial/Math Numeric Functions/LOG
LOG(X), LOG(B,X): If called with one parameter, this function returns the natural logarithm of X
mysql>
mysql> SELECT LOG(2);
+------------------+
| LOG(2) |
+------------------+
| 0.69314718055995 |
+------------------+
1 row in set (0.00 sec)
mysql>
mysql> SELECT LOG(-2);
+---------+
| LOG(-2) |
+---------+
| NULL |
+---------+
1 row in set (0.00 sec)
mysql>
Using LOG with data in a table
mysql>
mysql>
mysql> create table myTable(
-> id int(2),
-> value FLOAT(6,2)
-> );
Query OK, 0 rows affected (0.03 sec)
mysql>
mysql> insert into myTable(ID, value)values (1,9);
Query OK, 1 row affected (0.00 sec)
mysql> insert into myTable(ID, value)values (2,2.11);
Query OK, 1 row affected (0.00 sec)
mysql> insert into myTable(ID, value)values (3,3.44);
Query OK, 1 row affected (0.02 sec)
mysql> insert into myTable(ID, value)values (4,-4.21);
Query OK, 1 row affected (0.00 sec)
mysql> insert into myTable(ID, value)values (5,10);
Query OK, 1 row affected (0.00 sec)
mysql> insert into myTable(ID, value)values (6,3);
Query OK, 1 row affected (0.00 sec)
mysql> insert into myTable(ID, value)values (7,-5.88);
Query OK, 1 row affected (0.00 sec)
mysql> insert into myTable(ID, value)values (8,123.45);
Query OK, 1 row affected (0.01 sec)
mysql> insert into myTable(ID, value)values (9,98.23);
Query OK, 1 row affected (0.00 sec)
mysql> insert into myTable(ID, value)values (10,938.23);
Query OK, 1 row affected (0.00 sec)
mysql> insert into myTable(ID, value)values (11,-984.23);
Query OK, 1 row affected (0.00 sec)
mysql> insert into myTable(ID, value)values (12,198.23);
Query OK, 1 row affected (0.00 sec)
mysql> insert into myTable(ID, value)values (13,-928.87);
Query OK, 1 row affected (0.00 sec)
mysql> insert into myTable(ID, value)values (14,25.37);
Query OK, 1 row affected (0.00 sec)
mysql> insert into myTable(ID, value)values (15,-918.3);
Query OK, 1 row affected (0.00 sec)
mysql> insert into myTable(ID, value)values (16,9.23);
Query OK, 1 row affected (0.00 sec)
mysql> insert into myTable(ID, value)values (17,-8.23);
Query OK, 1 row affected (0.00 sec)
mysql>
mysql> select * from myTable;
+------+---------+
| id | value |
+------+---------+
| 1 | 9.00 |
| 2 | 2.11 |
| 3 | 3.44 |
| 4 | -4.21 |
| 5 | 10.00 |
| 6 | 3.00 |
| 7 | -5.88 |
| 8 | 123.45 |
| 9 | 98.23 |
| 10 | 938.23 |
| 11 | -984.23 |
| 12 | 198.23 |
| 13 | -928.87 |
| 14 | 25.37 |
| 15 | -918.30 |
| 16 | 9.23 |
| 17 | -8.23 |
+------+---------+
17 rows in set (0.00 sec)
mysql>
mysql> select value, LOG(value) from myTable;
+---------+------------------+
| value | LOG(value) |
+---------+------------------+
| 9.00 | 2.1972245773362 |
| 2.11 | 0.74668789777036 |
| 3.44 | 1.2354714880192 |
| -4.21 | NULL |
| 10.00 | 2.302585092994 |
| 3.00 | 1.0986122886681 |
| -5.88 | NULL |
| 123.45 | 4.8158361910706 |
| 98.23 | 4.587311701861 |
| 938.23 | 6.8439951006905 |
| -984.23 | NULL |
| 198.23 | 5.2894279511491 |
| -928.87 | NULL |
| 25.37 | 3.2335674066909 |
| -918.30 | NULL |
| 9.23 | 2.2224589989196 |
| -8.23 | NULL |
+---------+------------------+
17 rows in set (0.00 sec)
mysql>
mysql> drop table myTable;
Query OK, 0 rows affected (0.00 sec)
mysql>