ALLBASE/SQL Reference Manual (36216-90216)
212 Chapter7
Data Types
Overflow and Truncation
Overflow and Truncation
Some operations can result in data overflow or truncation. Overflow results in loss of data
on the left. Truncation results in loss of data on the right.
Overflow or truncation can occur in several instances as follows:
• During arithmetic operations, for example, when multiplication results in a number
larger than the maximum value allowable in its type. Arithmetic operations are defined
inChapter 8 , “Expressions.”
• When using aggregate functions, for example, when the sum of several numbers
exceeds the maximum allowable size of the type involved. Aggregate functions are
defined in Chapter 8 , “Expressions.”
• During type conversion, as when an INTEGER value is converted to a SMALLINT
value. Type conversion is discussed later in this chapter.
Because large integers (less than −2147483648 (−2
31
) or larger than 2147483647 (2
31
−1)
up to 15 digits long) are stored as decimals, large integer overflow actually results in a
DECIMAL OVERFLOW message.
Overflow always causes an error.
Truncation can cause a warning for the following types of data:
• Alphanumeric data—A warning occurs if a string is truncated because it is too long for
its target location. No error is given if truncation occurs on input.
• Numeric data—No error or warning occurs when zeroes are dropped from the left or
when any digit is dropped from the fractional part of DECIMAL or FLOAT values.
Otherwise, truncation of numeric values causes an error.
• LONG data—A warning occurs if LONG column data is truncated because it is too long
for its target input file. The output file location is modified to fit the LONG column
length, so no truncation error occurs on LONG column output. If the file system fills up,
or the limit of shared memory is reached, a system error occurs.
Refer to the ALLBASE/SQL Message Manual for information on handling warnings and
errors.
Underflow
Underflow occurs when a FLOAT or a REAL value is too close to zero to be represented by
the hardware. Underflow always causes an error.