MySQL 如何處理數值表達式評估期間的溢位？

As we know that MySQL will produce an error if overflow occurs during the assessment of numeric expressions. For example, the largest signed BIGNT is 9223372036857775807233720368577758072337203685 775

mysql> Select 9223372036854775807 + 1;
ERROR 1690 (22003): BIGINT value is out of range in '(9223372036854775807+1)'

MySQL can handle such kind of overflows in following ways:

BY CONVERTING VALUE TO UNSIGNED

#MySQL enables such kind of operations by converting the values to signed as foluns −

mysql> Select CAST(9223372036854775807 AS UNSIGNED) +1;
+------------------------------------------+
| CAST(9223372036854775807 AS UNSIGNED) +1 |
+------------------------------------------+
|                      9223372036854775808 |
+------------------------------------------+
1 row in set (0.07 sec)

透過使用精確值算術

MySQL可以使用精確值算術來處理上述表達式。這是因為溢出發生取決於操作數的範圍。例如，可以透過使用DECIMAL值來執行上述計算，如下所示−

mysql> Select 9223372036854775807.0 + 1;
+---------------------------+
| 9223372036854775807.0 + 1 |
+---------------------------+
|     9223372036854775808.0 |
+---------------------------+
1 row in set (0.01 sec)

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