SQL JOINS Concept
syed shabeer
0:00 / 0:00
SQL JOINS Concept
11 просмотров · 2 недели назад
syed shabeer
8 подписчиков
11 просмотров · 2 недели назад
Formula:
Cross join: M * N
Inner Join: M = N
Left Join: all M rows, matched N rows
Right join: Matched M rows, all N rows
Full outer join: Left join + Right join - Inner Join
Null = Null is always false
1 = Null is always false
Null usually means "i don't know".
'null' is string value, not null
