Bug #79260 Get "ERROR 1271: Illegal mix of collations" when comparing time and string
Submitted: 13 Nov 2015 7:33 Modified: 28 Nov 2019 21:41
Reporter: Su Dylan Email Updates:
Status: Closed Impact on me:
None 
Category:MySQL Server: DML Severity:S3 (Non-critical)
Version:5.7.8/5.6 OS:Any
Assigned to: CPU Architecture:Any

[13 Nov 2015 7:33] Su Dylan
Description:
Output:
=======
mysql> drop table t2; create table t2(a time(3), b varchar(100));
Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected (0.01 sec)

mysql> select a = b from t2;
ERROR 1271 (HY000): Illegal mix of collations for operation '='

Problem:
========
sucsess is expected.

How to repeat:
drop table t2; create table t2(a time(3), b varchar(100));
select a = b from t2;

Suggested fix:
The select should succeed.
[14 Nov 2015 4:11] MySQL Verification Team
Thank you for the bug report. I couldn't repeat with source server:

C:\dbs>c:\dbs\5.7\bin\mysql -uroot -p --port=3570 --prompt="mysql 5.7 > "
Enter password: ******
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.7.10 Source distribution PULL: 2015-NOV-07

Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql 5.7 > USE test
Database changed
mysql 5.7 > drop table t2; create table t2(a time(3), b varchar(100));
Query OK, 0 rows affected (0.02 sec)

Query OK, 0 rows affected (0.03 sec)

mysql 5.7 > select a = b from t2;
Empty set (0.00 sec)

C:\dbs>c:\dbs\5.6\bin\mysql -uroot --port=3560 -p --prompt="mysql 5.6 > "
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 5.6.28 Source distribution PULL: 2015-NOV-07

Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql 5.6 > USE test
Database changed
mysql 5.6 > drop table t2; create table t2(a time(3), b varchar(100));
Query OK, 0 rows affected (0.05 sec)

Query OK, 0 rows affected (0.03 sec)

mysql 5.6 > select a = b from t2;
Empty set (0.00 sec)

Anyway see bug https://bugs.mysql.com/bug.php?id=73552;
[16 Nov 2015 3:48] Su Dylan
Hi Miguel,

Thanks for the reply.
It turns out that it is related to charset 'utf8mb4'. Please use the following SQL statements to recreate.

Recreate:
=========
drop table t2; create table t2(a time(3), b varchar(100)) charset='utf8mb4';
select a = b from t2;

Output:
=======
mysql> drop table t2; create table t2(a time(3), b varchar(100)) charset='utf8mb4';
t a = b from t2;
Query OK, 0 rows affected (0.01 sec)

Query OK, 0 rows affected (0.01 sec)

mysql> select a = b from t2;
ERROR 1271 (HY000): Illegal mix of collations for operation '='
mysql> select version();
+-----------+
| version() |
+-----------+
| 5.7.8-rc  |
+-----------+
1 row in set (0.00 sec)
[16 Nov 2015 9:23] MySQL Verification Team
Thank you for the feedback.

C:\dbs>c:\dbs\5.7\bin\mysql -uroot -p --port=3570 --prompt="mysql 5.7 > "
Enter password: ******
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 5.7.10 Source distribution PULL: 2015-NOV-07

Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql 5.7 > use test
Database changed
mysql 5.7 > drop table t2; create table t2(a time(3), b varchar(100)) charset='utf8mb4';
Query OK, 0 rows affected (0.07 sec)

Query OK, 0 rows affected (0.07 sec)

mysql 5.7 > select a = b from t2;
ERROR 1271 (HY000): Illegal mix of collations for operation '='
[16 Nov 2015 9:39] MySQL Verification Team
5.6 affected too.
[28 Nov 2019 21:41] Roy Lyseng
Posted by developer:
 
Fixed in 5.7.29