SQL Tools(JOIN Operator(Inner join, Left join, Right join))

INNER JOIN Operator :-
INNER Join return all rows from the join of left table and right table if there are same data available in both tables if no data will match then it will return null
SELECT * FROM Table_Name_1 INNER JOIN Table_Name_2 WHERE Table_Name_1.Column_Name = Table_Name_2.Column_Name

You can divide your result in group like :-
If a table contains First_Name, Last_Name, Address, Ph_No and there are so many result according to First_Name then you can use Group_By Like this :-

SELECT * FROM Old_Persons As OP INNER JOIN New_Persons As NP WHERE OP.First_Name = NP.First_Name Group By OP.First_Name

LEFT JOIN Operator :-
LEFT join return all rows from the left table even there are no rows in right table.

SELECT * FROM Old_Persons As OP LEFT JOIN New_Persons As NP WHERE OP.First_Name = NP.First_Name Group By OP.First_Name

RIGHT JOIN Operator :-
RIGHT JOIN return all rows from the right table even if there are no rows available in left table.

SELECT * FROM Old_Persons As OP RIGHT JOIN New_Persons As NP WHERE OP.First_Name = NP.First_Name Group By OP.First_Name