If you enter a floating number that is too big or too small for the FLOAT data type, SQL Server 2005 will behave as:

* FLOAT(24) Underflow: If a floating number is too small for FLOAT(24), it will be stored as 0 without any warning.

* FLOAT(24) Overflow: If a floating number is too big for FLOAT(24), you will get an arithmetic overflow error.

* FLOAT(53) Underflow: If a floating number is too small for FLOAT(53), it will be stored as 0 with a warning.

* FLOAT(53) Overflow: If a floating number is too big for FLOAT(53), you will get a value-out-of-range error.

The tutorial exercise below some good underflow and overflow examples:

-- Single precision underflow without warning

DECLARE @x REAL; -- FLOAT(24)

SET @x = 9.234568E-39;

SELECT @x;

GO

0

-- Single precision overflow error

DECLARE @x REAL; -- FLOAT(24)

SET @x = 9.234568E+39;

GO

Msg 232, Level 16, State 2, Line 2

Arithmetic overflow error for type real,

value = 9234568000000000400000000000000000000000.000000.

-- Double precision underflow with warning

DECLARE @x FLOAT(53);

SET @x = 9.23456789012346E-309

SELECT @x;

GO

Warning: the floating point value '9.23456789012346E-309'

is too small. It will be interpreted as 0.

0

-- Double precision overflow error