Common MySQL Errors and How to Fix Them: A Practical Guide

MySQL Error 1: Can't connect to MySQL server on ‘localhost’ (10061)

Cause: MySQL service is not running on the host.

Solution: Start MySQL. If it fails, verify the my.ini (or my.cnf) configuration and correct any errors. To inspect current processes you can run:

mysqladmin -uroot -pYOUR_PASSWORD processlist

MySQL Error 2: Unknown MySQL Server Host ‘localhosadst’ (11001)

Cause: The hostname specified does not exist or cannot be resolved.

Solution: Edit the application’s configuration file (e.g., ./config.inc.php) and set $dbhost to a valid MySQL host address.

MySQL Error 3: Access denied for user ‘roota@localhost’ (Using password: YES)

Cause: Incorrect username or password.

Solution: Open ./config.inc.php and verify the values of $dbuser and $dbpw. Update them to the correct credentials and save.

MySQL Error 4: Access denied for user ‘red@localhost’ to database ‘newbbs’

Cause: The user lacks the required privileges (e.g., SELECT, UPDATE) on the target database.

Solution: Either grant the necessary rights to the user or use a different account with proper privileges. Example grant command:

GRANT ALL PRIVILEGES ON newbbs.* TO 'red'@'localhost' IDENTIFIED BY 'password';
FLUSH PRIVILEGES;

MySQL Error 5: No Database Selected

Cause: $dbname in the configuration points to a non‑existent database, or the user has no SELECT privilege on the database.

Solution: Verify that $dbname is correct and that the database exists. Ensure the MySQL user has at least SELECT permission on that database.

MySQL Error 6: Can’t open file ‘xxx_forums.MYI’ (errno: 145)

Cause: Table file is corrupted (e.g., abrupt shutdown, disk full) or file permissions are wrong after moving the data files.

Solution: Repair the MyISAM table using one of the following methods:

Command‑line: myisamchk -r /path/to/xxx_forums.MYI phpMyAdmin: select the table → Operations → “Repair table”.

Ensure the MySQL user can read/write the file (adjust ownership if necessary) and back up the database before repairing.

MySQL Error 7: Table ‘test.xxx_sessions’ doesn’t exist

Cause: The queried table is missing, often because a plugin or upgrade did not create it, or an incomplete backup was restored.

Solution: Follow the plugin’s installation guide to create the missing table, reinstall/upgrade the plugin, or manually execute the required CREATE TABLE statements.

MySQL Error 8: Unknown column ‘column_name’ in ‘field list’

Cause: The SQL statement references a column that does not exist in the target table—usually due to missing schema updates or version mismatches.

Solution: Apply the missing database migrations or modify the query to use existing columns.

MySQL Error 9: You have an error in your SQL syntax

Cause: Syntax errors introduced by custom plugin modifications or by importing a dump created with a newer MySQL version into an older server.

Solution: Locate the offending statement, correct the syntax, and re‑run. When dumping data for an older server, specify compatible character set options, e.g.:

mysqldump -uroot -p --default-character-set=latin1 --set-charset=gbk --skip-opt database > backup.sql

MySQL Error 10: Duplicate entry ‘xxx’ for key 1

Cause: A UNIQUE or PRIMARY key constraint is violated because the inserted value already exists. This often appears after upgrades that change index types.

Solution: Remove or modify the duplicate rows, or drop/recreate the index if uniqueness is not required. For AUTO_INCREMENT conflicts, set the next value higher than the current maximum.

MySQL Error 11: Duplicate key name ‘xxx’

Cause: An index with the same name already exists, typically during repeated upgrades.

Solution: If the existing index matches the intended definition, skip the CREATE INDEX statement; otherwise drop the existing index before creating the new one.

MySQL Error 12: Duplicate column name ‘xxx’

Cause: The column is being added again during an upgrade.

Solution: If the column definition matches the existing one, skip the ALTER TABLE … ADD COLUMN statement; otherwise drop the column first.

MySQL Error 13: Table ‘xxx’ already exists

Cause: The table already exists in the database.

Solution: If the existing table schema matches the desired one, skip the CREATE TABLE statement; otherwise drop the old table before recreating it.

MySQL Error 14: Can’t create database ‘xxx’. Database exists

Cause: Database names must be unique within a MySQL instance.

Solution: Rename the existing database or choose a different name for the new one.

MySQL Error 16: Unknown system variable ‘NAMES’

Cause: The MySQL version does not support the SET NAMES statement (character‑set setting).

Solution: Remove any SET NAMES '…' lines from the SQL script.

MySQL Error 17: Lost connection to MySQL server during query

Cause: Network interruptions or server overload cause the connection to drop while a query is executing.

Solution: Usually no immediate action is required. If the problem is frequent, consider improving hardware resources or optimizing slow queries.

MySQL Error 18: User ‘red’ has exceeded the ‘max_updates’ resource (current value: 500)

Cause: Per‑user limits in the mysql.user table (e.g., max_updates, max_questions, max_connections) have been exceeded.

Solution: On a dedicated server, edit the relevant fields in mysql.user and run FLUSH PRIVILEGES;. On shared hosting, contact the provider.

MySQL Error 19: Too many connections (1040)

Cause: The number of concurrent connections exceeds max_connections. A large wait_timeout can keep idle connections open, aggravating the issue.

Solution: Adjust MySQL configuration (e.g., my.cnf or my.ini) and restart MySQL:

[mysqld]
max_connections = 1000
wait_timeout = 10

On shared hosting, request higher limits from the provider.

MySQL Error 20: No such grant defined for user ‘%s’ on host ‘%s’ (error 1141)

Cause: The MySQL account does not have the required privileges.

Solution: Ensure the account is granted the necessary privileges (e.g., GRANT ALL ON db.* TO 'user'@'host';) or ask the server administrator to do so.

MySQL Error 21: Error on rename of ‘%s’ to ‘%s’ (errno: %d)

Cause: Insufficient privileges or missing ALTER rights when attempting to rename a table.

Solution: Verify that the MySQL user has ALTER privilege and correct the rename statement.

MySQL Error 22: Error reading file ‘%s’ (errno: %d)

Cause: MySQL cannot read the underlying table file (corruption, wrong ownership, or missing file).

Solution: On dedicated servers, check file ownership and integrity; on shared hosting, ask the provider to investigate.

MySQL Error 23: Host ‘*****’ is blocked because of many connection errors; unblock with ‘mysqladmin flush‑hosts’

Cause: MySQL has flagged the host as problematic after repeated connection failures.

Solution: Run mysqladmin flush-hosts (or restart MySQL). On shared hosting, contact the provider.

MySQL Error 24: Dropping database (can’t delete ‘%s’, errno: %d)

Cause: Insufficient DROP privileges or the database does not exist.

Solution: Ensure the MySQL account has the DROP privilege and that the database name is correct.

MySQL Error 25: Got error 28 from table handler (error 1030)

Cause: The storage volume for MySQL is full.

Solution: Free up disk space or request additional storage.

MySQL Error 26: Can’t create a new thread (error 11/35)

Cause: Server memory exhaustion or OS‑level corruption prevents MySQL from creating new threads.

Solution: Check memory usage, add RAM if needed, and investigate possible OS issues.

MySQL Error 27: Client does not support authentication protocol requested by server (error 1251)

Cause: The client version is older than the server (e.g., server 4.1+, client < 4.1).

Solution: Upgrade the client library or downgrade the stored password format, e.g.:

SET PASSWORD FOR 'user'@'host' = OLD_PASSWORD('newpwd');
-- or --
UPDATE mysql.user SET Password = OLD_PASSWORD('newpwd') WHERE User='user' AND Host='host';
FLUSH PRIVILEGES;

MySQL Error 28: Can’t connect to local MySQL server through socket ‘/var/lib/mysql/mysql.sock’ (error 2002)

Cause: MySQL is not running or the socket file path is incorrect.

Solution: Start MySQL. If the socket resides elsewhere, specify the full path in the client configuration, e.g.:

$dbhost = 'localhost:/tmp/mysql.sock';

MySQL Error 29: Can’t connect to MySQL server on ‘localhost’ (error 2003)

Cause: MySQL service is not running, often due to disk‑full conditions or incorrect basedir settings.

Solution: Ensure sufficient disk space, verify basedir and other paths in my.ini / my.cnf, then restart MySQL.

MySQL Error 30: Lost connection to MySQL server during query (error 2013)

Cause: Long‑running or inefficient queries cause the server to drop the connection.

Solution: Identify and optimise slow queries, disable problematic plugins, and consider upgrading server resources.

MySQL Error 31: Got a packet bigger than ‘max_allowed_packet’ bytes (error 1153)

Cause: The MySQL configuration limits packet size, which is exceeded (common after increasing upload limits).

Solution: Increase max_allowed_packet in the [mysqld] section of the configuration file, e.g.: max_allowed_packet = 10M Restart MySQL afterwards. On shared hosting, ask the provider to change the setting.