[MDEV-9318] ALTER to ENUM from INT,DOUBLE vs DECIMAL behave differently Created: 2015-12-23  Updated: 2018-06-13

Status: Open
Project: MariaDB Server
Component/s: OTHER
Affects Version/s: 5.5, 10.0, 10.1, 10.2
Fix Version/s: 10.2

Type: Bug Priority: Minor
Reporter: Alexander Barkov Assignee: Alexander Barkov
Resolution: Unresolved Votes: 0
Labels: None


 Description    

DROP TABLE IF EXISTS t1;
 
CREATE TABLE t1 (
 
  i INT,
 
  f DOUBLE,
 
  d DECIMAL(5,0)
 
) ENGINE=MyISAM;
 
INSERT INTO t1 VALUES (256,256,256);
 
SELECT * FROM t1;

returns

+------+------+------+
 
| i    | f    | d    |
 
+------+------+------+
 
|  256 |  256 |  256 |
 
+------+------+------+

i.e. three numbers with equal values.
Now if I ALTER all three fields to ENUM('256'), the results are different:

ALTER TABLE t1 MODIFY i ENUM('256'), MODIFY f ENUM('256'), MODIFY d ENUM('256');
 
SHOW WARNINGS;
 
SELECT * FROM t1;

returns:

+---------+------+----------------------------------------+
 
| Level   | Code | Message                                |
 
+---------+------+----------------------------------------+
 
| Warning | 1265 | Data truncated for column 'd' at row 1 |
 
+---------+------+----------------------------------------+
 
+------+------+------+
 
| i    | f    | d    |
 
+------+------+------+
 
| 256  | 256  |      |
 
+------+------+------+
 
1 row in set (0.00 sec)

It's not clear why INT and DOUBLE behave differently comparing to DECIMAL.
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