Some basic Oracle syntax

1. Connection

--- Internal connection
Select * From Dali. test1 A, Dali. Test2 B where a. A = B.;

--- Left join
Select * From Dali. test1 A, Dali. Test2 B where a. A = B. a (+ );

--- Right join
Select * From Dali. test1 A, Dali. Test2 B where a. a (+) = B.;

--- Full connection
Select * From Dali. test1 A, Dali. Test2 B where a. A = B. a (+)
Union
Select * From Dali. test1 A, Dali. Test2 B where a. a (+) = B.;

--- Dikar
Select * From Dali. test1, Dali. Test2;

 

 

Judge whether it is null:
Isnull (field1, 0) in SQL Server)
Nvl (field1, 0) in Oracle)