How Can I Count Rows Meeting Specific Conditions Within a COUNT() Function?

Conditional Counting Within COUNT() Functions

You can incorporate conditions directly into your COUNT() function. This is particularly useful when you need to count rows meeting different criteria within a single SQL query, avoiding the need for multiple queries or subqueries. For example, counting the number of "Managers" and "Employees" in a single SELECT statement.

The key is to use a CASE expression within the COUNT() function. COUNT() only counts non-NULL values. Therefore:

<code class="language-sql">SELECT COUNT(CASE WHEN Position = 'Manager' THEN 1 ELSE NULL END) AS ManagerCount
FROM ...</code>

This counts only rows where the Position is 'Manager'. The ELSE NULL ensures that rows not meeting the condition are not counted.

Alternatively, you can use SUM():

<code class="language-sql">SELECT SUM(CASE WHEN Position = 'Manager' THEN 1 ELSE 0 END) AS ManagerCount
FROM ...</code>

This achieves the same result; SUM() adds 1 for each 'Manager' and 0 for all others. This approach can be slightly more efficient in some database systems. Both methods avoid the need for a separate WHERE clause, making them ideal for counting multiple categories concurrently.

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