DOUBLE_PRECISION or DOUBLE scalar function
The DOUBLE_PRECISION and DOUBLE functions return a doubleprecision floatingpoint representation of either a number or a string representation of a number.
Numeric to DOUBLE
String to DOUBLE
The schema is SYSIBM.
 Numeric to DOUBLE

 numericexpression
 An expression that returns a value of any
builtin numeric data type.
The result is the same number that would occur if the argument were assigned to a doubleprecision floatingpoint column or variable. If the numeric value of the argument is not within the range of doubleprecision floatingpoint, an error is returned (SQLSTATE 22003).
 String to DOUBLE

 stringexpression
 An expression that returns a string, including FOR BIT DATA, that
represents a number. The data type of this expression cannot be CLOB, BLOB, or DBCLOB (SQLSTATE
42884).
The result is the same number that would result from the statement
CAST(stringexpression AS DOUBLE PRECISION)
. Leading and trailing blanks are eliminated and the resulting string must conform to the rules for forming a valid numeric constant (SQLSTATE 22018). If the numeric value of the argument is not within the range of doubleprecision floatingpoint, an error is returned (SQLSTATE 22003).
The result of the function is a doubleprecision floatingpoint number. If the argument can be null, the result can be null; if the argument is null, the result is the null value.
Notes
 The CAST specification should be used to increase the portability of applications.
 FLOAT is a synonym for DOUBLE_PRECISION and DOUBLE.
 The SYSFUN version of DOUBLE (string_expression) continues to be available.
Example
SELECT EMPNO, DOUBLE(SALARY)/COMM
FROM EMPLOYEE
WHERE COMM > 0