COUNT(*) vs. COUNT(Column-Name): When Should I Use Which Aggregate Function?

COUNT(*) vs COUNT(Column-Name): Determining the Appropriate Aggregate Function

In SQL, determining which aggregate function to use between COUNT() and COUNT(column-name) is an essential aspect of data retrieval. Whether the choice of COUNT() or COUNT(column-name) matters hinges on the desired result.

COUNT(*) calculates the total number of rows in a result set, regardless of whether specific columns contain NULL values. In contrast, COUNT(column-name) only counts non-NULL values within the specified column.

To further clarify:

• COUNT(*): Encompasses all rows, including those with NULL values.
• COUNT(column-name): Excludes rows with NULL values in the specified column.
• COUNT(1): Functionally equivalent to COUNT(*) since 1 represents a non-NULL expression.

The appropriate function to employ depends solely on the intended output. If you seek a total count of all rows, regardless of NULL values, COUNT(*) suffices. However, if you aim to count only non-NULL values in a specific column, COUNT(column-name) is the preferred choice.

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