Spanner supports the following MySQL numeric functions.You need to implement the MySQL functions in yourSpanner database before you can use them. For more information oninstalling the functions, seeInstall MySQL functions.

Function list

mysql.DEGREES

mysql.DEGREES(numeric_expression)

Description

Converts an angle value from radians to degrees.

This function supports the following argument:

• numeric_expression: The angle in radians, specified as aFLOAT64 value.

Return data type

FLOAT64

Limitations

If you provide a very large input value (greater than approximately 1e300), thefunction may result in an overflow error.

Example

The following example converts π radians to degrees:

SELECTmysql.DEGREES(ACOS(-1))aspi_in_degrees;/*+---------------+| pi_in_degrees |+---------------+| 180.0         |+---------------+*/

mysql.LOG2

mysql.LOG2(numeric_expression)

Description

Calculates the base-2 logarithm of a numeric value.

This function supports the following argument:

• numeric_expression: TheFLOAT64 value for which to calculate the base-2 logarithm.

Return data type

FLOAT64

Limitations

The input valuenumeric_expression must be greater than zero. Ifnumeric_expression is zero or negative, thefunction returnsNULL.

Example

The following example calculates the base-2 logarithm of 8:

SELECTmysql.LOG2(8)ASlog2_of_8;/*+-----------+| log2_of_8 |+-----------+| 3.0       |+-----------+*/

mysql.PI

mysql.PI()

Description

Returns the mathematical constant pi (π).

This function doesn't support any arguments.

Return data type

FLOAT64

Example

The following example returns the value of π:

SELECTmysql.PI()aspi_value;/*+-------------------+| pi_value          |+-------------------+| 3.141592653589793 |+-------------------+*/

mysql.RADIANS

mysql.RADIANS(numeric_expression)

Description

Converts an angle value from degrees to radians.

This function supports the following argument:

• numeric_expression: The angle in degrees, specified as aFLOAT64 value.

Return data type

FLOAT64

Example

The following example converts 180 degrees to radians:

SELECTmysql.RADIANS(180)asradians_value;/*+-------------------+| radians_value     |+-------------------+| 3.141592653589793 |+-------------------+*/

mysql.TRUNCATE

mysql.TRUNCATE(numeric_expression,precision)

Description

Truncates a number to a specified number of decimal places. This functiondoes not perform rounding.

This function supports the following arguments:

• numeric_expression: TheFLOAT64 value to truncate.
• precision: TheINT64 value specifying the number of decimal places to preserve.Ifprecision is positive, it truncates toprecision decimal places. Ifprecision is zero, ittruncates to the nearest whole number towards zero. Ifprecision is negative, itmakesprecision digits to the left of the decimal point zero.

Return data type

FLOAT64

Differences from MySQL

This function's behavior with two arguments,numeric_expression (the number) andprecision (the number of decimalplaces), is similar to MySQL'sTRUNCATE(numeric_expression, precision) function.

Limitations

TRUNCATE is a reserved keyword. If you use this function in Data DefinitionLanguage (DDL) statements, such as in generated column definitions, you mustenclose the function name in backticks (for example,mysql.`TRUNCATE`).

Example

The following example demonstrates various uses of theTRUNCATE function:

SELECTmysql.TRUNCATE(123.4567,2)astruncate_2_decimals,mysql.TRUNCATE(123.987,0)astruncate_to_integer,mysql.TRUNCATE(123.456,-1)astruncate_tens_place,mysql.TRUNCATE(-123.456,1)astruncate_negative_num;/*+---------------------+---------------------+---------------------+-----------------------+| truncate_2_decimals | truncate_to_integer | truncate_tens_place | truncate_negative_num |+---------------------+---------------------+---------------------+-----------------------+| 123.45              | 123.0               | 120.0               | -123.4                |+---------------------+---------------------+---------------------+-----------------------+*/