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分享mysql 數據庫中 double 型態計算問題
select amount from money;
看到結果是 : 3.52
而我用常數 3.52 和其比較時確說不相等. 難道mysql的double精度有問題?
看到結果是 : 3.52
而我用常數 3.52 和其比較時確說不相等. 難道mysql的double精度有問題?
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skyairmj 2006-07-20
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转化成string,然后再进行比较
hy2003fly 2006-07-20
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旧的版本,double类型的数据存储不是精确的,例如:
Before MySQL 5.0.3, numbers that are treated as floating-point values produce inexact results:
mysql> SELECT .1 + .2 = .3;
+--------------+
| .1 + .2 = .3 |
+--------------+
| 0 |
+--------------+
As of MySQL 5.0.3, numbers are used as given when possible:
mysql> SELECT .1 + .2 = .3;
+--------------+
| .1 + .2 = .3 |
+--------------+
| 1 |
+--------------+
Before MySQL 5.0.3, numbers that are treated as floating-point values produce inexact results:
mysql> SELECT .1 + .2 = .3;
+--------------+
| .1 + .2 = .3 |
+--------------+
| 0 |
+--------------+
As of MySQL 5.0.3, numbers are used as given when possible:
mysql> SELECT .1 + .2 = .3;
+--------------+
| .1 + .2 = .3 |
+--------------+
| 1 |
+--------------+
trainee 2006-07-20
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浮点型的比较都有这问题
