15.00 - LN - Teradata Database

LN

Purpose  

Computes the natural logarithm of the argument.

Syntax  

where:

Syntax element …	Specifies …
arg	a nonzero, positive numeric argument.

ANSI Compliance

This is a Teradata extension to the ANSI SQL:2011 standard.

Result Type and Attributes

The data type, format, and title for LN(arg) are as follows.

Data Type	Format	Title
FLOAT	Default format for FLOAT	LN(arg)

For information on default data type formats, see SQL Data Types and Literals.

Argument Types and Rules

If arg is not FLOAT, it is converted to FLOAT based on implicit type conversion rules. If the argument cannot be converted, an error is reported. For more information on implicit type conversion, see “Implicit Type Conversions” on page 583.

If arg is a UDT, the following rules apply:

The UDT must have an implicit cast to any of the following predefined types:

Numeric

Character

DATE

To define an implicit cast for a UDT, use the CREATE CAST statement and specify the AS ASSIGNMENT clause. For more information on CREATE CAST, see SQL Data Definition Language.

Implicit type conversion of UDTs for system operators and functions, including LN, is a Teradata extension to the ANSI SQL standard. To disable this extension, set the DisableUDTImplCastForSysFuncOp field of the DBS Control Record to TRUE. For details, see Utilities: Volume 1 (A-K).

LN cannot be applied to the following types of arguments:

BYTE or VARBYTE

BLOB or CLOB

CHARACTER or VARCHAR if the server character set is GRAPHIC

Examples  

Representative LN arithmetic function expressions and the results are as follows.

Expression	Result
LN(2.71828182845905)	1.00000000000000E+000
LN(0)	Error