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PostgreSQL WHERE

The WHERE clause in PostgreSQL is used to filter records in a query based on specific conditions. Only rows that meet the condition(s) are returned.

Key Topics

1. Basic Syntax

SELECT *
FROM table_name
WHERE condition;

Replace condition with a valid expression (e.g., salary > 50000).

2. Using Logical Operators

Combine multiple conditions with AND or OR:

SELECT first_name, department
FROM employees
WHERE department = 'Sales' AND salary >= 40000;

Best Practices

  • Index columns that are frequently used in WHERE clauses for faster queries.
  • Use parameterized queries in applications to prevent SQL injection.

Key Takeaways

  • WHERE is essential for filtering data in SELECT, UPDATE, and DELETE statements.
  • Logical operators refine the query to narrow or broaden the result set.
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