Difference between 2 dates, in week boundaries, for MySql

f_weekdiff.sql

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CREATE FUNCTION f_weekdiff(expr1 DATETIME, expr2 DATETIME)
RETURNS INTEGER
COMMENT 'Returns the number of week boundaries between expr1 and expr2. Example: f_weekdiff(\'2019-10-07\', \'2019-09-30\'); == 1'
DETERMINISTIC
LANGUAGE SQL
BEGIN
    SET expr1 = ADDDATE(expr1, -1 * WEEKDAY(expr1)); -- "moves" expr1 to the beggining of its week
    SET expr2 = ADDDATE(expr2, -1 * WEEKDAY(expr2)); -- "moves" expr2 to the beggining of its week

    RETURN DATEDIFF(expr1, expr2) / 7;
END;

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