What Is The Difference Between Count * And Count 1 In Spark SQL?

Have you observed that the SQL COUNT() method exists in several variants? The several justifications and their applications are clarified in this paper.

You most likely know the COUNT() method really well as a SQL user. Though it's really basic, there are various ways you might apply it. Every approach serves a rather distinct purpose. I assume you have encountered code including either COUNT(*) or COUNT(1). Though you have not personally used them, you have most likely also seen several other applications of the COUNT() function, such COUNT(column name) and Count(*) vs Count(1) in SQL).

You most likely want to know what every variation of COUNT() performs. Let us know!

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What purpose does the COUNT() Function serve?

The COUNT() function counts as one could expect. But ultimately, what counts? SQL's aggregate functions include the COUNT() one. It counts the rows meeting the conditions stated in the parenthesis. It displays the number of rows that satisfy your criteria, not the rows themselves.

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Count(*:) vs Count(1)

Different debates on the variations between COUNT(*) and COUNT(1) have probably come across you. And perhaps looking for the solution puzzled you much more. In other words, is there any variation? The straightforward response is no; there is not at all any difference.

Including null values, the COUNT(*) function counts the overall rows in the table. The semantics for Counters(1) vary somewhat; we will go over them later. The numbers for COUNT(*) and COUNT(1) are exactly the same, though.

Let's examine this assertion with a hypothetical query. Assuming I have a table called orders with these columns:

order_id is the order's ID.
customer_id: The ID of the order-placing customer.
Order value: The ordered products' combined euro value.
The payment date is the day the consumer paid the order.
Using the COUNT() function in the following manner would help me to determine the total table's rows count:

SELECT COUNT(*) AS number_of_rows
FROM orders;

Count() vs Count() with a column name

Regarding this one, COUNT(*) against COUNT(column name), Does anyone notice any differences? There absolutely is!

COUNT(*) will count every row in the table—including NULL values—as you well know. Conversely, CENTS(column name) will count all the rows in the designated column omitting NULL values.

The table has eight rows, as you already know. The orders follow Using the column order_id for counting—imagining I want to know how many orders have been placed—let's examine how many rows there will be. We shall once more obtain eight rows. Let us see:

SELECT COUNT(order_id) AS number_of_orders
FROM orders;