Mysql十进制: floor instead of round

Question

在我的 MySQL 数据库中，我有字段 DECIMAL(23,5)，所以小数点后有 5 位数字。现在，当我这样查询时:

UPDATE my_table SET my_decimal_field = 123.123456789 WHERE id = 1

然后我将获取该记录:

SELECT id, my_decimal_field FROM gijhars WHERE id = 1

我得到这个结果:

+------+------------------+
| id   | my_decimal_field |
+------+------------------+
| 5733 |   123.12346      |
+------+------------------+

因此，如果小数点后超过 6 位，MySQL 当然会舍入这些值。 MySQL 中是否有任何设置floor 这些值而不是四舍五入？

Answer 1

来自 doc

When such a column is assigned a value with more digits following the decimal point than are permitted by the specified scale, the value is converted to that scale. (The precise behavior is operating system-specific, but generally the effect is truncation to the permissible number of digits.)

如果您的操作系统不是这种情况，那么您可以在使用 truncate 更新时处理此问题

UPDATE my_table 
SET my_decimal_field = truncate(123.123456789, 5) 
WHERE id = 1

SQLFiddle demo