Mysql投到十進制給99.9

Question

我得到一個varchar字段說的值爲174，但是當我cast(field as decimal(3,1))它給我總是99.9？我如何投射或將其轉換爲17.4？或者我必須在源代碼級更改要以十進制輸入的輸入嗎？

Answer 1

這是因爲174不能用小數點前2位和小數點後1位表示。 decimal(3,1)小數點後的意思是「總共3位和1（3）

mysql> select cast('174' as decimal(3,1)); 
+-----------------------------+ 
| cast('174' as decimal(3,1)) | 
+-----------------------------+ 
|      99.9 | 
+-----------------------------+ 
1 row in set, 1 warning (0.00 sec) 

它給出了可以與示出的警告：

mysql> show warnings; 
+---------+------+----------------------------------------------------------------------+ 
| Level | Code | Message                | 
+---------+------+----------------------------------------------------------------------+ 
| Warning | 1264 | Out of range value for column 'cast('174' as decimal(3,1))' at row 1 | 
+---------+------+----------------------------------------------------------------------+ 
1 row in set (0.00 sec) 

除以10，並嘗試數目再次：

mysql> select cast('174'/10 as decimal(3,1)); 
+--------------------------------+ 
| cast('174'/10 as decimal(3,1)) | 
+--------------------------------+ 
|       17.4 | 
+--------------------------------+ 
1 row in set (0.00 sec)