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Summary: Learn how to efficiently update table rows in PostgreSQL using subqueries. This guide covers the syntax and examples to help you master this powerful SQL technique.
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Updating Table Rows in PostgreSQL Using Subquery

When working with PostgreSQL, there are situations where you need to update rows in a table based on the results from a subquery. Subqueries can be powerful tools to perform complex updates, allowing you to refine the data manipulation process. This post will guide you through the syntax and provide examples to help you understand how to update table rows using subqueries in PostgreSQL.

Basic Syntax

In PostgreSQL, an UPDATE statement with a subquery typically follows this structure:

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Example Scenario

Consider two tables: employees and departments. You want to update the salary of employees based on the budget of their respective departments.

Tables

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Updating Employee Salaries

Let's say you want to set the salary of each employee to be 10% of their department's budget. You can achieve this using a subquery:

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Subqueries in the WHERE Clause

Subqueries can also be used in the WHERE clause to update specific rows. For instance, if you only want to update employees in departments with a budget greater than $1,000,000, you can use:

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Using FROM Clause with Subqueries

PostgreSQL allows using the FROM clause in the UPDATE statement, which can sometimes simplify the query and improve readability. Here’s an example:

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Conclusion

Updating table rows using subqueries in PostgreSQL provides a flexible and powerful way to manipulate data. By understanding and leveraging subqueries in your UPDATE statements, you can perform more complex and refined data updates. Practice with different scenarios to become proficient in using this technique in your SQL workflows.