Average Without @avg | Dataford Interview Questions

If you did not have the AVG function, how would you find the average for cells A1-A10?

Assume the cells are stored as rows in PostgreSQL. Treat NULL cell values as blank cells that should be excluded from the calculation, and return NULL if every selected cell is blank.

Output

Return one row with one column named average_value.
Calculate the result only from cells A1 through A10.
Return the average as a numeric value rounded to four decimal places.

Schema

spreadsheet_cells

Column	Type	Description
cell_idPK	INT	Unique identifier for the stored cell
cell_label	VARCHAR(10)	Spreadsheet-style cell label
cell_value	NUMERIC(12,4)	Numeric value stored in the cell, or NULL for a blank cell

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