In SQL Server, the T-SQL LOG10() function is a mathematical function that returns the base-10 logarithm of the specified float expression.
You specify the float expression as an argument.
Syntax
The syntax goes like this:
LOG10 ( float_expression )
Where float_expression is an expression of type float or of a type that can be implicitly converted to float.
Example 1 – Basic Usage
Here’s a basic example to demonstrate how this function works.
SELECT LOG10(10) Result;
Result:
+----------+ | Result | |----------| | 1 | +----------+
And here’s another example using various values.
SELECT LOG10(100) '100', LOG10(1000) '1000', LOG10(3000) '3000', LOG10(10000) '10000';
Result:
+-------+--------+------------------+---------+ | 100 | 1000 | 3000 | 10000 | |-------+--------+------------------+---------| | 2 | 3 | 3.47712125471966 | 4 | +-------+--------+------------------+---------+
Example 2 – Negative Value
Here’s an example of passing in a negative value.
SELECT LOG10(-4) Result;
Result:
Msg 3623, Level 16, State 1, Line 1 An invalid floating point operation occurred.
This example returns an error message because the logarithm can only be returned for positive numbers that aren’t 1.
Example 3 – Zero
Here’s an example of passing in zero as the argument (we get the same result as the previous example).
SELECT LOG10(0) Result;
Result:
Msg 3623, Level 16, State 1, Line 1 An invalid floating point operation occurred.
Example 4 – Passing in 1
Passing in a value of 1 returns zero.
SELECT LOG10(1) Result;
Result:
+----------+ | Result | |----------| | 0 | +----------+
Example 5 – Expressions
You can also pass in expressions like this:
SELECT LOG10(5*2) Result;
Result:
+----------+ | Result | |----------| | 1 | +----------+
That’s effectively the same as doing this:
SELECT LOG10(10) Result;
Result:
+----------+ | Result | |----------| | 1 | +----------+
LOG()
Transact-SQL also has the LOG() function which returns the natural logarithm of a number.
In fact, you can use LOG() instead of LOG10() if you prefer. To do this, use 10 as the second argument to the function. Example below.
SELECT LOG(100, 10) 'LOG', LOG10(100) 'LOG10';
Result:
+-------+---------+ | LOG | LOG10 | |-------+---------| | 2 | 2 | +-------+---------+