153. Deep dive into window functions. Part 2: Grouping and counting with percentage

Let’s continue our tour of window functions. Window functions are always followed up by an OVER() clause where we can specify how to group or partition rows for calculations.

⚠ We also can omit any partitioning. In this case we’ll just leave OVER() clause empty and for each row its group or partition will be the entire table.

⚠ Just a reminder that window functions are calculated in SELECT statement. It means all filters from WHERE have been applied. So entire table in the previous paragraph ☝ and further means not the initial raw table with all the...

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