Check out example codes for "sql compare data from two tables". It will help you in understanding the concepts better.

Code Example 1

-- Oracle

-- Example
SELECT * 
FROM Table1 -- the table containing extra records
  MINUS
  SELECT * 
  FROM Table2;

-- Syntax 
SELECT * 
FROM <table-1> -- the table containing extra records
  MINUS
  SELECT * 
  FROM <table-2>;

Code Example 2

select * from tableA
minus
select * from tableB

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