Error
Error Code:
1110
MariaDB Error 1110: Duplicate Column in Query
Description
Error 1110 indicates that a column name has been specified more than once within a SQL statement where uniqueness is required. This commonly occurs in `SELECT`, `INSERT`, `CREATE TABLE`, or `ALTER TABLE` statements when defining or referencing columns.
Error Message
Column '%s' specified twice
Known Causes
4 known causesDuplicate SELECT Columns
A column name is listed multiple times in the `SELECT` clause of a query, which is not allowed.
Repeated GROUP BY/ORDER BY Column
The same column name appears more than once in the `GROUP BY` or `ORDER BY` clause, leading to redundancy and an error.
Duplicate Column in Table Definition
When creating or altering a table, the same column name is used for two different columns within the table definition.
Repeated INSERT Columns
A column name is specified more than once in the column list of an `INSERT` statement, indicating redundant data mapping.
Solutions
3 solutions available1. Identify and Remove Duplicate Column in SELECT Clause easy
Locate the repeated column name in your SELECT statement and remove one instance.
1
Examine the SQL query that is producing the MariaDB Error 1110.
2
Look specifically at the `SELECT` clause. The error message will indicate the duplicate column name (e.g., `Column 'user_id' specified twice`).
3
Identify the column that appears more than once in the `SELECT` list.
4
Remove one of the duplicate column specifications. If you need to select the column with an alias, ensure the alias is unique and the original column is listed only once.
SELECT id, name, email, email AS user_email FROM users;5
If you intended to select the same column with different aliases, remove the redundant selection of the original column.
SELECT id, name, email AS primary_email, email AS secondary_email FROM users;6
Re-run the corrected query.
2. Address Duplicate Columns in `GROUP BY` or `ORDER BY` Clauses easy
Ensure column names are unique within `GROUP BY` and `ORDER BY` clauses.
1
Review the SQL query, paying close attention to the `GROUP BY` and `ORDER BY` clauses.
2
Check if the same column name is listed multiple times within either of these clauses.
SELECT COUNT(*) FROM orders GROUP BY customer_id, customer_id;3
Remove the redundant column specification from the `GROUP BY` or `ORDER BY` clause.
SELECT COUNT(*) FROM orders GROUP BY customer_id;4
If you are using aliases, ensure they are unique and correctly referenced.
SELECT customer_id, COUNT(*) AS order_count FROM orders GROUP BY customer_id ORDER BY order_count, customer_id DESC;5
Re-execute the query.
3. Investigate Subqueries and Joins for Duplicate Column Definitions medium
Examine subqueries and join conditions for unintended duplicate column selections.
1
If your query involves subqueries or joins, carefully inspect the `SELECT` list within each subquery and the main query.
2
Look for instances where a column from a joined table is selected in both the main query's `SELECT` clause and a subquery's `SELECT` clause, especially if the column name is not qualified with a table alias.
SELECT u.id, o.id FROM users u JOIN orders o ON u.id = o.user_id WHERE o.id IN (SELECT id FROM orders WHERE order_date > '2023-01-01');3
Qualify column names with table aliases to disambiguate them. Ensure each selected column, even if it's the same logical piece of data, is specified only once in the final output of the query or subquery.
SELECT u.id, o.id AS order_id FROM users u JOIN orders o ON u.id = o.user_id WHERE o.id IN (SELECT id FROM orders WHERE order_date > '2023-01-01');4
If a subquery is returning a column that is also explicitly selected in the outer query, consider if the subquery's selection is necessary or if it can be removed or modified.
5
Test the modified query.