Common SQL Errors and How to Fix Them
Browse all documented SQL errors with detailed explanations, root causes, and step-by-step fixes.
Cannot drop table 'employees' because related table 'salaries' does not exist
This error occurs when trying to drop a table that has a foreign key constraint referencing another table, but that refe…
ERROR at line 5: ORA-00936: missing expression
This error occurs when the database expects an expression but doesn't receive one. In SQL, an expression is a combinatio…
SQLSTATE[22P02]: Invalid text representation: 7 ERROR: invalid input syntax for
This error occurs when you try to store a non-numeric value in a column that is defined as an integer. In this case, the…
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 …
Cannot access object property 'connection' on a null value in query execution bl
This error occurs when the framework or library being used to execute SQL queries is unable to properly connect to the d…
Invalid column reference in the ORDER BY clause near 'id, name'
This error occurs when the database is unable to parse the SQL syntax, specifically in this case, when the ORDER BY clau…
Invalid parameter type: expected array for 'where' clause, got string
This error occurs when the SQL framework expects an array of parameters for the 'where' clause, but a string is passed i…
SQLSTATE[42S22]: Column not found: 1054 Unknown column 'username' in 'field list
This error occurs when you try to select a column that does not exist in the table. This can happen when you misspell th…
SQLSTATE[HY000][2002] Can't connect to local MySQL server through socket '/var/r
This error occurs when the SQL client is unable to connect to the MySQL server. It typically happens when the MySQL serv…
SQLSTATE[HY000] [2002] Connection to MySQL server at 'localhost:3306' failed: un
This error occurs when the MySQL connection fails due to a certificate verification issue. It usually happens when the s…
near ";" at character 12: unexpected token: ";". Expected "AS".
This error occurs when SQL parser encounters a syntax that it does not expect, in this case, an unexpected semicolon (";…
Incorrect syntax near 'JOIN'. Expecting 'FROM' keyword
This error occurs when the SQL parser encounters a JOIN operation without a preceding FROM keyword, violating the SQL sy…
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