Error Reference

SQL Errors & Debugging

Quick solutions for common SQL errors. Find your error message, understand why it happens, and fix it with working code examples.

Pro tip: Use Ctrl+F (or Cmd+F) to search for your specific error message on this page.

Browse by Category

Syntax Errors

Query structure and keyword issues

Group By Error

Reference Errors

Missing or incorrect references

Column Not Found Ambiguous Column

Constraint Violations

Data integrity issues

Duplicate Key

Data Type Errors

Type mismatch and conversion issues

Data Type Mismatch Division By Zero

Performance Issues

Timeout and resource problems

Lock Wait Timeout Lock Wait Timeout Deadlock Detected

Access Errors

Permission and connection issues

Permission Denied

All SQL Errors

Mysql Error: Ambiguous Column

Fix ambiguous column error in mysql. Step-by-step solution with code examples.

Mysql Error: Cannot Insert Null

Fix cannot insert null error in mysql. Step-by-step solution with code examples.

Mysql Error: Column Not Found

Fix column not found error in mysql. Step-by-step solution with code examples.

Mysql Error: Duplicate Key

Fix duplicate key error in mysql. Step-by-step solution with code examples.

Mysql Error: Invalid Syntax

Fix invalid syntax error in mysql. Step-by-step solution with code examples.

Postgresql Error: Ambiguous Column

Fix ambiguous column error in postgresql. Step-by-step solution with code examples.

Postgresql Error: Cannot Insert Null

Fix cannot insert null error in postgresql. Step-by-step solution with code examples.

Postgresql Error: Column Not Found

Fix column not found error in postgresql. Step-by-step solution with code examples.

Postgresql Error: Duplicate Key

Fix duplicate key error in postgresql. Step-by-step solution with code examples.

Postgresql Error: Invalid Syntax

Fix invalid syntax error in postgresql. Step-by-step solution with code examples.

SQL Error: Ambiguous Column (Fix + Examples)

Fix the SQL "column reference "column_name" is ambiguous" error. Learn what causes it and see examples of how to resolve it.

SQL Error: Cannot Insert Null (Fix + Examples)

Fix the SQL "null value in column "column_name" violates not-null constraint" error. Learn what causes it and see examples of how to resolve it.

SQL Error: Column Not Found (Fix + Examples)

Fix the SQL "column "column_name" does not exist" error. Learn what causes it and see examples of how to resolve it.

SQL Error: Connection Refused (Fix + Examples)

Fix the SQL "could not connect to server: Connection refused" error. Learn what causes it and see examples of how to resolve it.

SQL Error: Data Type Mismatch (Fix + Examples)

Fix the SQL "column "column_name" is of type X but expression is of type Y" error. Learn what causes it and see examples of how to resolve it.

SQL Error: Deadlock Detected (Fix + Examples)

Fix the SQL "deadlock detected" error. Learn what causes it and see examples of how to resolve it.

SQL Error: Division By Zero (Fix + Examples)

Fix the SQL "division by zero" error. Learn what causes it and see examples of how to resolve it.

SQL Error: Duplicate Key (Fix + Examples)

Fix the SQL "duplicate key value violates unique constraint" error. Learn what causes it and see examples of how to resolve it.

SQL Error: Foreign Key Constraint (Fix + Examples)

Fix the SQL "insert or update on table violates foreign key constraint" error. Learn what causes it and see examples of how to resolve it.

SQL Error: Group By Error (Fix + Examples)

Fix the SQL "column must appear in the GROUP BY clause or be used in an aggregate function" error. Learn what causes it and see examples of how to resolve it.

SQL Error: Invalid Syntax (Fix + Examples)

Fix the SQL "syntax error at or near "keyword"" error. Learn what causes it and see examples of how to resolve it.

SQL Error: Lock Wait Timeout (Fix + Examples)

Fix the SQL "canceling statement due to lock timeout" error. Learn what causes it and see examples of how to resolve it.

SQL Error: Permission Denied (Fix + Examples)

Fix the SQL "permission denied for table table_name" error. Learn what causes it and see examples of how to resolve it.

SQL Error: String Truncation (Fix + Examples)

Fix the SQL "value too long for type character varying(N)" error. Learn what causes it and see examples of how to resolve it.

SQL Error: Subquery Returns Multiple Rows (Fix + Examples)

Fix the SQL "more than one row returned by a subquery used as an expression" error. Learn what causes it and see examples of how to resolve it.

Sqlserver Error: Ambiguous Column

Fix ambiguous column error in sqlserver. Step-by-step solution with code examples.

Sqlserver Error: Cannot Insert Null

Fix cannot insert null error in sqlserver. Step-by-step solution with code examples.

Sqlserver Error: Column Not Found

Fix column not found error in sqlserver. Step-by-step solution with code examples.

Sqlserver Error: Duplicate Key

Fix duplicate key error in sqlserver. Step-by-step solution with code examples.

Sqlserver Error: Invalid Syntax

Fix invalid syntax error in sqlserver. Step-by-step solution with code examples.

General Debugging Tips

Read the Error Message

SQL error messages usually tell you exactly what went wrong. Look for line numbers, column names, or table references in the message.

Check Your Syntax

Missing commas, unclosed quotes, or misspelled keywords are common culprits. Review your query character by character.

Verify Object Names

Ensure table and column names exist and are spelled correctly. Case sensitivity varies by database.

Test in Parts

For complex queries, test each part separately. Start with the FROM clause and add clauses one at a time.

Database-Specific Guides

MySQL Errors

Database-specific error codes and solutions

Coming Soon

PostgreSQL Errors

Database-specific error codes and solutions

Coming Soon

SQL Server Errors

Database-specific error codes and solutions

Coming Soon