Shulou(Shulou.com)06/01 Report--

# you can compare if you can sort, and ignore the null values SELECT MAX (last_name), MIN (last_name), COUNT (last_name) FROM employees;#count can only calculate the number that is not null SELECT COUNT (commission_pct) FROM employees;# ignores null values SELECT SUM (commission_pct), AVG (commission_pct) FROM employees;# and deduplicates SELECT SUM (DISTINCT salary), SUM (salary) FROM employees;#distinct deduplicates SELECT COUNT (DISTINCT salary), COUNT (salary) FROM employees

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