self join query in sql. 15 objective questions. What is equi join and outer jo

self join query in sql.
15 objective questions.
What is equi join and outer join

Question Posted / reshma

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self join query in sql. 15 objective questions. What is equi join and outer join..

Answer / swaroopa

What is Equi Join and Outer Join ?

Equi Joins are also called Simple Joins or Inner Joins.
An equi-join is a join based on equality or matching
between the column values for two different tables.

This equality is indicated with an equal sign (=) as the
comparison operator in the WHERE clause

Ex:SELECT * FROM manufact, stock
WHERE manufact.manu_code = stock.manu_code

manufact and stock are the tables on the manu_code column.
It retrieves only those rows for which the values of the
two columns are equal.

Outer Join:

OUTER JOIN is used to join two tables even if there is not
a match. The joined table retains each record—even if no
other matching record exists. Outer joins subdivide further
into left outer joins, right outer joins, and full outer
joins, depending on which table(s) one retains the rows
from (left, right, or both).

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self join query in sql. 15 objective questions. What is equi join and outer join..

Answer / latha

self join:one physical table is divided into two logical tables and perform join operation on that tables.
query:
select a.eno,a.ename,b.ename as manager name from emp a,emp b where a.manager num=b.eno
equi join:perform join operations on matching columns on both the tables

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