sql - MySQL functions COUNT/MIN/MAX issue -

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i run following queries sum same answer

sql 1 ::

select l_partkey,sum(l_linenumber)  lineitem  inner join orders on orders.o_orderkey = lineitem.l_orderkey   o_weekday='tuesday'  group l_partkey

sql 2 ::

select sum(if(orders.o_weekday='tuesday',l_linenumber, 0)) 'tuesday'  lineitem  inner join orders on orders.o_orderkey = lineitem.l_orderkey group  lineitem.l_partkey

but when run above queries avg/count/min/max function instead of sum both queries gives different output.

say have following data:

monday    1 tuesday   2 tuesday   3

your first query looks @ last 2 rows. sum 5, average 2.5, number of lines 2.

your second query looks @ rows. first row, replaces number 1 0. sum still 5, average 5/3, , number of lines 3.

for sum, rows value of 0 not matter. rows 0 influence other aggregates count, min, max , avg.


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