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Description

Error 1248 occurs in MariaDB when a subquery used in the FROM clause (known as a derived table) is not assigned an explicit alias. MariaDB requires every derived table to have a unique alias for proper referencing and query execution.

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Error Message

Every derived table must have its own alias

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Known Causes

3 known causes

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Missing Alias in Subquery

The most common cause is simply forgetting to add the `AS alias_name` part immediately after a subquery within the `FROM` clause.

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Complex Nested Derived Tables

In queries involving multiple levels of nested derived tables, it can be easy to overlook assigning an alias to one of the inner subqueries.

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Unadapted SQL Snippets

Copying and pasting SQL code from examples or other database systems that might not enforce derived table aliases, without making the necessary adjustments for MariaDB.

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Solutions

3 solutions available

1. Assign an Alias to the Derived Table easy

The most direct solution is to provide a name for your derived table.

1

Locate the `SELECT` statement that is causing the error. This statement will contain a subquery (a query within another query) that is being treated as a derived table.

2

Immediately after the closing parenthesis of the derived table's `SELECT` statement, add a space and then the desired alias (a name for this derived table).

SELECT ... FROM (SELECT column1 FROM your_table) AS derived_table_alias;

3

If you reference columns from this derived table in the outer query, use the alias followed by a dot and the column name (e.g., `derived_table_alias.column1`).

SELECT dt.column1 FROM (SELECT column1 FROM your_table) AS dt WHERE dt.column1 > 10;

2. Use a Common Table Expression (CTE) Instead medium

For more complex queries, CTEs offer better readability and organization than derived tables.

1

Identify the derived table in your query.

2

Rewrite the query using a CTE. Start with the `WITH` keyword, followed by the CTE name, an opening parenthesis, your derived table's `SELECT` statement, a closing parenthesis, and then the main query that references the CTE.

WITH cte_name AS (
  SELECT column1 FROM your_table
)
SELECT column1 FROM cte_name WHERE column1 > 10;

3

Ensure the CTE name is unique and descriptive.

3. Review and Simplify Subqueries medium

Sometimes, the error indicates an overly complex or incorrectly structured subquery that might be simplified or rewritten.

1

Analyze the subquery that is being used as a derived table. Understand its purpose and the data it is intended to return.

2

If the subquery is very complex, consider breaking it down into smaller, more manageable parts. This might involve creating temporary tables or using multiple CTEs.

3

Ensure that the subquery is a valid `SELECT` statement and that it's correctly enclosed in parentheses.

4

After ensuring the subquery is correctly formed, apply Solution 1 to assign an alias.

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Related Errors

5 related errors

MariaDB Error 1248: Derived Table Alias Required