How to Fix the 'Subquery Returns More Than 1 Row' Error in SQL?

Overcoming the "Subquery Returns More Than 1 Row" Error

When working with subqueries, it's not uncommon to encounter the frustrating error "subquery returns more than 1 row." This issue arises when a subquery is expected to return a single value but instead yields multiple rows. To resolve this error and successfully execute your query, it's crucial to understand the proper usage of subqueries.

In the given example, a subquery is employed to return multiple rows, which is then referenced in the main query to set the id field. However, this approach results in the aforementioned error because = can only evaluate a subquery that returns a single value.

To resolve this issue, you should utilize the IN operator instead, which is designed to evaluate subqueries that return multiple values. By using IN, you can specify that the id field should match any of the values returned by the subquery.

Here's an example that demonstrates the correct usage of IN:

SELECT *
FROM table
WHERE id IN (multiple row query);

For instance, if the subquery returns the values 1, 2, and 3, the id field will be set to 1 or 2 or 3, effectively filtering the results based on the multiple values returned by the subquery.

By using IN, you can effectively handle subqueries that return multiple rows, ensuring that your query executes successfully without encountering the "subquery returns more than 1 row" error.

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