COUNT(*) vs. COUNT(column-name): When Should I Use Each?

When to Use COUNT(*) vs. COUNT(column-name)

In SQL, both COUNT(*) and COUNT(column-name) are commonly used aggregate functions to count the number of rows in a dataset. However, there are subtle differences between them.

COUNT(*)

COUNT(*) counts all rows in a table or specified set, regardless of whether individual columns have NULL values. Essentially, it counts the entire row, including any empty cells.

COUNT(column-name)

COUNT(column-name) counts only the non-NULL values in a specific column. If a row has a NULL value in the specified column, it will not be included in the count.

Specific Use Cases

• Use COUNT(*) when you want to count all rows, regardless of whether they contain NULL values. This is often used for overall row counts or when you are not concerned with specific columns.
• Use COUNT(column-name) when you want to count only the non-NULL values in a specific column. This is useful when you want to analyze the distribution of data or identify rows with missing information.

Additional Points

• COUNT(1) is equivalent to COUNT(*) because 1 is a non-NULL expression.
• Your choice between COUNT(*) and COUNT(column-name) should solely depend on the desired output and the specific context of your query.

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