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PostgreSQL Fetch Data

Data retrieval in PostgreSQL is primarily done using the SELECT statement. You can filter, sort, and aggregate results to fit your application needs.

Key Topics

1. Basic SELECT Syntax

SELECT column1, column2, ...
FROM table_name;

Use * to select all columns.

2. Filtering with WHERE

SELECT *
FROM employees
WHERE salary > 50000;

The WHERE clause filters rows based on a condition, returning only those that satisfy the specified criterion.

3. Sorting and Limiting Results

Use ORDER BY to sort data, and LIMIT to retrieve a specified number of rows.

SELECT first_name, last_name, salary
FROM employees
ORDER BY salary DESC
LIMIT 5;

Code Explanation: This query sorts employees by salary in descending order, returning only the top 5 results.

Best Practices

  • Use appropriate indexes to speed up data retrieval on frequently searched columns.
  • Avoid using SELECT * in production queries to reduce unnecessary data transfer.
  • Combine ORDER BY and LIMIT for pagination when displaying data in applications.

Key Takeaways

  • PostgreSQL's SELECT is flexible for retrieving specific columns or entire rows.
  • WHERE clauses and other filters help narrow down the results.
  • Sorting and limiting results are essential for performance and user-friendly data presentation.
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