Interview Question

What is COUNT()?

COUNT(*) counts rows; COUNT(expression) counts non-null expression values.

💡 Concept ✅ Quick Revision 🗃️ SQL

Answer

COUNT returns the number of qualifying inputs. • COUNT(*) counts rows. • COUNT(expression) counts rows where the expression is not NULL. • COUNT(DISTINCT expression) counts distinct non-null values.

💡 SQL Example

SELECT COUNT(*) AS employee_count FROM employees;

Result

7

⚡ Quick Revision

COUNT(*) counts rows; COUNT(expression) counts non-null expression values.

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