Short Notes on MySQL
Error 1045: Access denied
The 1045 bug may appear under many circumstances, and it may be related to multiple problems.
Kind of "legacy" problem might be that there is anonymous user defined. Such user will show up with empty Name in the following set:
mysql> select User, Host, Password from mysql.user; +-------------+----------------+-------------------------------------------+ | User | Host | Password | +-------------+----------------+-------------------------------------------+ | root | localhost | [.................hash..................] | | root | 127.0.0.1 | [.................hash..................] | | | % | [.................hash..................] | | ... | +-------------+----------------+-------------------------------------------+
This user will be selected first, and will interfere with your login. Removing such user is generally a good idea anyways.
Next problem, when connecting remotely, may be caused simply by networking being disabled, or that MySQL binds only to local IP.
show variables like 'skip_networking'; +-----------------+-------+ | Variable_name | Value | +-----------------+-------+ | skip_networking | ON | +-----------------+-------+
You can either set this variable to OFF, or comment out the setting in /etc/mysql/my.cnf:
# skip-networking
One more option is that your MySQL server binds only to local IP; under [mysqld] section in /etc/mysql/my.cnf comment out bind setting, or replace it with your public IP:
# bind-address = 127.0.0.1 # or bind-address = 123.1.2.3
If none of this helps, you're left with user privileges. Make sure the user that is trying to connect is at all present in system:
mysql> select User, Host, Password from mysql.user; +-------------+----------------+-------------------------------------------+ | User | Host | Password | +-------------+----------------+-------------------------------------------+ | ... | +-------------+----------------+-------------------------------------------+
If it is (make sure both User and Host match, or Host is %), make sure it has rights granted:
show grants for 'dbuser'@'example.com';
If the user does not exist, or if it doesn't have rights granted, you can create and/or update it at once with:
grant all on db.* to 'dbuser'@'example.com' identified by 'password';
Of course, restrict the grant all to just rights required whenever possible.
Also, make sure to include the identified by 'password' each time, otherwise, if the user does not exist in system, it'll be left with empty password.
One last thing - make sure individual users with the same username have the same password (if this is desirable):
mysql> select User, Host, Password from mysql.user where User = 'dbuser'; +-------------+----------------+-------------------------------------------+ | User | Host | Password | +-------------+----------------+-------------------------------------------+ | dbuser | localhost | [.................hash..................] | | dbuser | 127.0.0.1 | [.................hash..................] | | dbuser | example.com | | +-------------+----------------+-------------------------------------------+
Note that 'dbuser'@'example.com' has empty password! It's just as possible that the hashes/passwords differ. To fix this, use
set password for 'dbuser'@'example.com' = PASSWORD('password');
After all this, you should be able to connect... hopefully.
Note: You can also
flush privileges;
after updates to the user grants and passwords, but this is rarely necessary unless you're on a MySQL Cluster.
The insert ... on duplicate key update Pitfall
Some time back I had a problem - gaps in values in auto_increment column in MySQL table.
It turns out that when using insert ... on duplicate key update, the auto_increment counter is being incremented even if the row exists, and is only being updated.
If you want the auto_increment column to be contiguous, or simply don't wanna waste values available, you'll have to check if the row exists and use insert/update accordingly.
This might especially become a problem in tables where updates to rows are much more frequent than inserts, and you might run out of values for the ID column.
