MySQL Bugs: #79538: Update query that should syntax error gets executed improperly.

Bug #79538	Update query that should syntax error gets executed improperly.
Submitted:	6 Dec 2015 15:11	Modified:	6 Dec 2015 16:42
Reporter:	Brandon Johnson	Email Updates:
Status:	Duplicate	Impact on me:	None
Category:	MySQL Server: Parser	Severity:	S2 (Serious)
Version:	5.6.22	OS:	Any
Assigned to:		CPU Architecture:	Any

Description:
Accidentally running a multi-column update query with AND instead of comma separated values and it executes, but silently doesn't update the latter columns.

How to repeat:
mysql> create table test_table(a int, b int, c int);
Query OK, 0 rows affected (0.02 sec)

mysql> insert into test_table() values(1,1,1);
Query OK, 1 row affected (0.00 sec)

mysql> update test_table set a=null and b=null and c=null;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from test_table;
+------+------+------+
| a    | b    | c    |
+------+------+------+
| NULL |    1 |    1 |
+------+------+------+
1 row in set (0.00 sec)

Suggested fix:
Fix the parser to accurately identify that it won't do anything for the latter columns.

Ultimately this is an expression evaluation problem, but since it can be syntactically recognized as an impossible expression, I reported it to the parser category.

Thank you for the bug report. Duplicate of http://bugs.mysql.com/bug.php?id=6583.