Returns the arctangent of x and y coordinates as an angle expressed in radians.
The x and y coordinates are specified by the first and second arguments, respectively.

The schema is SYSIBM. (The SYSFUN version of the ATAN2 function continues to be available.)

expression1

An expression that returns a value of any built-in numeric data type except for DECFLOAT.
The value is converted to a double-precision floating-point number for processing by the function.

expression2

An expression that returns a value of any built-in numeric data type except for DECFLOAT.
The value is converted to a double-precision floating-point number for processing by the function.

The result of the function is a double-precision floating-point number.
The result can be null if the argument can be null or the database is configured with dft_sqlmathwarn set to YES;
the result is the null value if the argument is null.