Computer systems use internal registers to performs math functions.
These registers are typically 32-bit, 64-bit, 128-bit, or 256-bit in length.
DOUBLE PRECISION gives a double-precision floating-point number (the size of two registers).

> The actual precision of DOUBLE PRECISION depends on the RDBMS vendor’s implementation.

> Since it is a floating-point number expressed in scientific notation, it is an approximate number and may not be accurate to the last digit.

> It can be negative, zero, or positive.

> If you have a choice between exact (DECIMAL or NUMERIC) or approximate (FLOAT, REAL, or DOUBLE PRECISION), use the exact data type because you get completely accurate numbers and it processes faster.

> SQL:2003 introduced REAL, DOUBLE PRECISION, and FLOAT(precisionbits) data types.
> Approximate data type should be used only for very extreme ranges of numeric values.