These are some Microsoft Excel functions that I find useful:
XLOOKUP: Given a key, find its matching index in an array and retrieve a value at same index from another array.
XLOOKUP(lookup_value, lookup_array, return_array)
DSUM: Sum the cells that meet certain conditions. Inputs are the table, the column from which to sum and the cells with conditions.
MATCH: Given a key value and a row of cells, find relative position of cell in those cells that matches the key.
NETWORKDAYS: To count the number of workdays between a start date and an end date, excluding weekdays and holidays.
A1 has the start date and
A2 has the end date.