Union and intersection

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3. Union and Intersection
Zabeeb anwar
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4. union
AUB
- AUB(OR) means the union of sets A and B
contains all of the elements of both A and B.

5. Intersection
AÇB(AND) means the intersection of sets A
and B. This contains all of the elements which
are in both A and B.

6. Union and Intersection with empty

7. Union and Intersection in Psql

8. Union
- A hot startup is holding a special event and
wants to send out invites for my marriage()
to some of my best clients and also to some
VIPs.
- Some of the VIPs are actually very supportive
of the site and are clients too.
- What query will provide the complete set of
people to invite avoiding duplicate records?
- Here is our data.

9. Union
• create database hotstartup;
• create table clients(name varchar);
insert into clients values(‘Sharan');
insert into clients values(‘Vineesh');
insert into clients values(‘Bala');
insert into clients values(‘Sheethal');
• create table vips(name varchar);
insert into vips values(‘Reshmi');
insert into vips values(‘Sheethal');
insert into vips values(‘Anupa');
insert into vips values(‘Ashwathy');

10. Union
• hotstartup=# select * from clients union select *
from vips;
name
----------------
Sharan
Vineesh
Bala
Sheethal
Reshmi
Anupa
Ashwathy
(7 rows)

11. Union All
• hotstartup=# select * from clients union all select * from vips;
name
----------------
Sharan
Vineesh
Bala
Sheethal
Reshmi
sheethal
Anupa
Ashwathy
(8 rows)

12. Intersect
• if I want to get the list of people who are both
clients and VIP we can use INTERSECT.
• hotstartup=# select * from
clients intersect select * from vips;
name
----------------
Sheethal
(1 row)

13. Intersect All
• Let's insert a Sheethal(duplicate name) into VIP’s.
name
----------------
Sharan
Vineesh
Bala
Sheethal
Sheethal
(4 rows)
-select * from client intersect all select * from vips;

14. Intersect All
name
----------------
sheethal
sheethal
(2 rows)
- Sheethal appears in both tables twice so we
find two matching pairs for her and hence two
rows appears in the results.

15. Except
• I want everyone on the clients list EXCEPT those on
the VIP list.
• select * from clients except select * from vips;
name
----------------
Sharan
Vineesh
Bala

16. Except All
• Let's insert a Sheethal(duplicate name) into clients.
name
----------------
Sharan
Vineesh
Bala
Sheethal
Sheethal
(4 rows)
-select * from clients except all select * from vips;

17. Except All
name
----------------
Sharan
Vineesh
Bala
Sheethal
(4 rows)

18. Where Clause
• select * from Clients_Year;
name | Birth year
------------------+------
Sharan | 1976
Vineesh | 1977
Bala | 1978
Ashwathy | 1983
Reshmi | 199 3
sheethal | 1996
Anupa | 1997

19. Where Clause
• select * from clients_year where year
between 1970 and 1979 union select * from
ceos where year=1977;
name | Birth year
------------------+------
Sharan | 1976
Vineesh | 1977
Bala | 1978

20. Do not
• select * from clients where year between
1970 and 1979 union select name from clients
where year=1977;
ERROR: each UNION query must have the
same number of columns

21. Union and intersection in Python

22. Example
>>>engineers = Set(['John', 'Jane', 'Jack',
'Janice'])
>>>programmers = Set(['Jack', 'Sam', 'Susan',
'Janice'])
>>>managers = Set(['Jane', 'Jack', 'Susan',
'Zack'])

23. Union
>>>employees = engineers | programmers |
managers
>>>print “employees”
Set(['Jane', 'Janice', 'John’,
'Jack’,’susan’,’Zack’,’sam’])

24. Intersection
>>>engineers = Set(['John', 'Jane', 'Jack',
'Janice'])
>>>managers = Set(['Jane', 'Jack', 'Susan',
'Zack'])
>>>engineering_management = engineers &
managers
>>>print “engineering_management”
Set(['Jane', 'Jack’])

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