This error occurs when a column name referenced in your query exists in multiple joined tables, and MySQL cannot determine which table the column comes from. Qualify column names with table or alias prefixes to resolve the ambiguity.
MySQL error 1052 (ER_NON_UNIQ_ERROR) indicates that a column name in your SQL query is ambiguous because it exists in two or more tables being joined together. When MySQL processes the query, it cannot determine which table's version of the column you intend to use. This typically happens in SELECT, JOIN, WHERE, or ORDER BY clauses where the same column name appears in multiple tables without explicit table qualification. The database requires you to clarify your intent by prefixing the column name with its table name or alias.
Use the DESCRIBE command to list all columns in each table involved in your query:
DESCRIBE employees;
DESCRIBE departments;Look for columns with the same name across tables (common examples: id, status, name, created_at).
Prefix each ambiguous column with its table name or alias. Instead of:
SELECT id, name FROM employees JOIN departments ON department_id = department_id;Use:
SELECT employees.id, employees.name FROM employees JOIN departments ON employees.department_id = departments.department_id;Assign short aliases to table names to make qualification easier to read:
SELECT e.id, e.name, d.location
FROM employees e
JOIN departments d ON e.department_id = d.department_id;Aliases are defined after the table name (e.g., employees e) and can be used throughout the query.
Review every part of your query for unqualified column references:
SELECT e.id, e.status -- Qualify in SELECT
FROM employees e
JOIN departments d ON e.id = d.id -- Qualify in JOIN ON
WHERE e.status = 'active' -- Qualify in WHERE
ORDER BY e.created_at; -- Qualify in ORDER BYEnsure consistency throughout the entire query.
If both tables use identical column names for the join, use the USING clause:
SELECT e.id, e.name, d.location
FROM employees e
JOIN departments d USING (department_id);This tells MySQL the column comes from both tables and outputs it only once, reducing ambiguity. However, explicit table qualification is generally preferred for clarity.
Best practice is to qualify ALL column names with table aliases, even if no ambiguity exists. This makes queries more readable, easier to maintain, and prevents errors if columns are added to tables later. When self-joining a table (e.g., to find parent-child relationships), always use distinct aliases: SELECT parent.id, child.id FROM categories parent JOIN categories child ON child.parent_id = parent.id. In ORM frameworks like Sequelize, TypeORM, or Doctrine, this is usually handled automatically, but raw SQL queries require manual qualification.
ERROR 1064: You have an error in your SQL syntax
How to fix "ERROR 1064: You have an error in your SQL syntax" in MySQL
ERROR 1054: Unknown column in field list
Unknown column in field list
ER_WINDOW_RANGE_FRAME_NUMERIC_TYPE (3589): RANGE frame requires numeric ORDER BY expression
RANGE frame requires numeric ORDER BY expression in MySQL window functions
CR_ALREADY_CONNECTED (2058): Handle already connected
How to fix "CR_ALREADY_CONNECTED (2058): Handle already connected" in MySQL
ER_WINDOW_DUPLICATE_NAME (3591): Duplicate window name
How to fix ER_WINDOW_DUPLICATE_NAME (3591) in MySQL window functions