COALESCE
NULLIF
to_jsonb
jsonb_agg
array_agg


FILTER: 
SELECT sum(id) FILTER (where id % 2 = 1) FROM cs;

NTH_VALUE -- https://www.postgresqltutorial.com/postgresql-nth_value-function/
FIRST_VALUE/LAST_VALUE

RANK / DENSE_RANK 
[1/1/3/3/5  1/1/2/2/3]
RANK() OVER (
    [PARTITION BY partition_expression, ... ]
    ORDER BY sort_expression [ASC | DESC], ...
)
NTILE (n) OVER (...)	-- Similar to Rank, but most Nth value, as average as possible  => Rank: 1/2/3/4/5   Ntile(3) => 1/1/2/2/3/  Like Level ?

ROW_NUMBER (1/2/3/4...)
ROW_NUMBER() OVER(
    [PARTITION BY column_1, column_2,…]
    [ORDER BY column_3,column_4,…]
)

--Last Nth row value! 	https://www.postgresqltutorial.com/postgresql-lag-function/
LAG(expression [,offset [,default_value]]) 
OVER (
    [PARTITION BY partition_expression, ... ]
    ORDER BY sort_expression [ASC | DESC], ...
)
SELECT
	year, 
	amount,
	group_id,
	LAG(amount,1) OVER (
		PARTITION BY group_id
		ORDER BY year
	) previous_year_sales
FROM
	sales;

--Next Nth row value!	https://www.postgresqltutorial.com/postgresql-lead-function/
LEAD(expression [,offset [,default_value]]) 
OVER (
    [PARTITION BY partition_expression, ... ]
    ORDER BY sort_expression [ASC | DESC], ...
)



--Fetch(Replacement of Limit) https://www.postgresqltutorial.com/postgresql-fetch/
FETCH FIRST/NEXT 1 ROW ONLY; 	== LIMIT 1

OFFSET 5 ROWS 
FETCH FIRST 5 ROW ONLY;     == LIMIT 5, 5