Common SQL Errors and How to Fix Them
Browse all documented SQL errors with detailed explanations, root causes, and step-by-step fixes.
SQLSTATE[HY000] [1045] Unable to connect to the database: Access denied for user
This error occurs when the database connection fails due to authentication issues, usually caused by incorrect database …
ORA-01502: index contains duplicate key values starting from row 1
This error occurs when trying to create an index on a column that contains duplicate values. In an index, each value mus…
Error converting data type nvarchar to datetime. Caught at SQL Server procedure
This error occurs when SQL Server encounters a datetime value that cannot be converted from a string to a datetime forma…
Cannot create index 'idx_user_email': key must be unique but exists in index 'id
This error occurs when you try to create a new index on a column that already exists and is defined as unique, but the i…
Cannot use an index on a table that has not been fully joined: 'SELECT * FROM em
This error occurs when SQL is unable to use an index on a table that is not fully joined due to the presence of a correl…
Call to undefined method 'createTable' for object of class 'PDO' in /var/www/htm
The error occurs when attempting to use a method that is not supported by the database object. This can happen when upgr…
Cannot add foreign key constraint 'fk_orders_customers' because table 'orders' d
This error occurs when you're trying to add a foreign key constraint to a table, but the referenced table does not exist…
Invalid value for column 'age' of type 'integer': '<b>NULL</b>'
This error occurs when the database encounters an unexpected value in a column. In this case, it is trying to insert a '…
Cannot generate system views for recursive common table expressions (CTEs) with
This error occurs when a database is unable to create an internal system view for a recursive Common Table Expression (C…
Cannot truncate table 'sales' because it is being referenced by a FOREIGN KEY co
This error occurs when you try to truncate a database table, but that table has a foreign key relationship with another …
SQLSTATE[HY000]: General error: 1216 Cannot delete or update a parent row: a for
This error occurs when attempting to delete or update a record in a table that has a foreign key relationship with anoth…
Cannot execute query due to configuration mismatch: Unable to locate 'connection
This error occurs when the application's configuration settings do not match the expected settings required by the SQL f…
Have a SQL error that's not listed? Get an instant explanation.
Explain Another Error