SELECT s.StudentID, s.StudentName
FROM tClass c 
INNER JOIN tstudent s ON c.ClassID = s.ClassID
WHERE c.ClassID = 10

So above query is used to fetch the list of students which are studying in Class – “10th”. So here in “tstudent” table all students are stored irrespective of their classes and similarly in “tclass” table all classes are stored. So as the result of the above query, matched records between tstudent and tclass tables are searched and displayed. In the introduction part there was an introduction to the term called “predicate”, in the above query it is – “ON c.ClassID = s.ClassID”, which is one of the essential part of the join.

Left Join
Left join will return all the rows from the left table and matching rows from right table.
In case of no match with right side table it will return NULL value.
“Left Join” and “Left Outer Join” are used interchangeably because records which are returned will be the same with either of these.
Below query is used to fetch the all the classes and the students are in that class.
SELECT s.StudentID, s.StudentName
FROM tClass c 
LEFT JOIN tstudent s ON c.ClassID = s.ClassID