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11.2.6 Out-of-Range and Overflow Handling
When MySQL stores a value in a numeric column that is outside the permissible range of the column data type, the result depends on the SQL mode in effect at the time:
If strict SQL mode is enabled, MySQL rejects the out-of-range value with an error, and the insert fails, in accordance with the SQL standard.
If no restrictive modes are enabled, MySQL clips the value to the appropriate endpoint of the column data type range and stores the resulting value instead.
When an out-of-range value is assigned to an integer column, MySQL stores the value representing the corresponding endpoint of the column data type range.
When a floating-point or fixed-point column is assigned a value that exceeds the range implied by the specified (or default) precision and scale, MySQL stores the value representing the corresponding endpoint of that range.
Suppose that a table t1
has this definition:
With strict SQL mode enabled, an out of range error occurs:
With strict SQL mode not enabled, clipping with warnings occurs:
- +---------+------+---------------------------------------------+
- | Level | Code | Message |
- +---------+------+---------------------------------------------+
- +---------+------+---------------------------------------------+
- +------+------+
- | i1 | i2 |
- +------+------+
- | 127 | 255 |
- +------+------+
When strict SQL mode is not enabled, column-assignment
conversions that occur due to clipping are reported as warnings
for ALTER TABLE
,
LOAD DATA
,
UPDATE
, and multiple-row
INSERT
statements. In strict
mode, these statements fail, and some or all the values are not
inserted or changed, depending on whether the table is a
transactional table and other factors. For details, see
Section 5.1.11, “Server SQL Modes”.
Overflow during numeric expression evaluation results in an
error. For example, the largest signed
BIGINT
value is
9223372036854775807, so the following expression produces an
error:
To enable the operation to succeed in this case, convert the value to unsigned;
- +-------------------------------------------+
- +-------------------------------------------+
- | 9223372036854775808 |
- +-------------------------------------------+
Whether overflow occurs depends on the range of the operands, so
another way to handle the preceding expression is to use
exact-value arithmetic because
DECIMAL
values have a larger
range than integers:
- +---------------------------+
- | 9223372036854775807.0 + 1 |
- +---------------------------+
- | 9223372036854775808.0 |
- +---------------------------+
Subtraction between integer values, where one is of type
UNSIGNED
, produces an unsigned result by
default. If the result would otherwise have been negative, an
error results:
- Query OK, 0 rows affected (0.00 sec)
If the NO_UNSIGNED_SUBTRACTION
SQL mode is enabled, the result is negative:
- +-------------------------+
- +-------------------------+
- | -1 |
- +-------------------------+
If the result of such an operation is used to update an
UNSIGNED
integer column, the result is
clipped to the maximum value for the column type, or clipped to
0 if NO_UNSIGNED_SUBTRACTION
is enabled. If strict SQL mode is enabled, an error occurs and
the column remains unchanged.
Document created the 26/06/2006, last modified the 26/10/2018
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