[#MDEV-6780] Regression select @var := behavior from MySQL 5.5

There is a difference between MariaDB's behavior and MySQL 5.5 when a query is doing select @var := count(*). MySQL would return the number of rows matched while Maria returns 0.. Its unclear to me which behavior is actually correct.

While I personally wouldn't have used the := syntax here, someone else did and it broke our application a little bit..

drop database if exists `test_example`;

create database test_example;

use test_example;

CREATE TABLE `blarg` (

  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,

  `v` varchar(10),

  PRIMARY KEY (`id`)

) ENGINE=InnoDB;

insert into blarg (`v`) values ('AAA');

insert into blarg (`v`) values ('AAA');

insert into blarg (`v`) values ('AAA');

insert into blarg (`v`) values ('BBB');

insert into blarg (`v`) values ('BBB');

insert into blarg (`v`) values ('CCC');

MariaDB [test_example]> select count(*), @a := count(*), v from blarg group by v;

+----------+----------------+------+

| count(*) | @a := count(*) | v    |

+----------+----------------+------+

|        3 |              0 | AAA  |

|        2 |              0 | BBB  |

|        1 |              0 | CCC  |

+----------+----------------+------+

3 rows in set (0.00 sec)

mysql> select count(*), @a := count(*), v from blarg group by v;

+----------+----------------+------+

| count(*) | @a := count(*) | v    |

+----------+----------------+------+

|        3 |              3 | AAA  |

|        2 |              2 | BBB  |

|        1 |              1 | CCC  |

+----------+----------------+------+

3 rows in set (0.00 sec)

mysql>

[MDEV-6780] Regression select @var := behavior from MySQL 5.5 Created: 2014-09-24 Updated: 2014-10-10 Resolved: 2014-09-26
Status:	Closed
Project:	MariaDB Server
Component/s:	OTHER
Affects Version/s:	5.5.37
Fix Version/s:	10.0.6

[MDEV-6780] Regression select @var := behavior from MySQL 5.5 Created: 2014-09-24 Updated: 2014-10-10 Resolved: 2014-09-26