Union and intersection
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Union and intersection Union and intersection Presentation Transcript

  • Disclaimer: This presentation is prepared by trainees ofbaabtra as a part of mentoring program. This is not officialdocument of baabtra –Mentoring PartnerBaabtra-Mentoring Partner is the mentoring division of baabte System Technologies Pvt .Ltd
  • Union and IntersectionZabeeb anwarzabeebanwar@gmail.comwww.fb.com/zabeebanwartwitter.com/zabeebanwarin/linkedin.com/in/zabeeb9895599689
  • unionAUB- AUB(OR) means the union of sets A and Bcontains all of the elements of both A and B.
  • IntersectionAÇB(AND) means the intersection of sets Aand B. This contains all of the elements whichare in both A and B.
  • Union and Intersection with empty
  • Union and Intersection in Psql
  • Union- A hot startup is holding a special event andwants to send out invites for my marriage()to some of my best clients and also to someVIPs.- Some of the VIPs are actually very supportiveof the site and are clients too.- What query will provide the complete set ofpeople to invite avoiding duplicate records?- Here is our data.
  • 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);
  • Union• hotstartup=# select * from clients union select *from vips;name----------------SharanVineeshBalaSheethalReshmiAnupaAshwathy(7 rows)
  • Union All• hotstartup=# select * from clients union all select * from vips;name----------------SharanVineeshBalaSheethalReshmisheethalAnupaAshwathy(8 rows)
  • Intersect• if I want to get the list of people who are bothclients and VIP we can use INTERSECT.• hotstartup=# select * fromclients intersect select * from vips;name----------------Sheethal(1 row)
  • Intersect All• Lets insert a Sheethal(duplicate name) into VIP’s.name----------------SharanVineeshBalaSheethalSheethal(4 rows)-select * from client intersect all select * from vips;
  • Intersect Allname----------------sheethalsheethal(2 rows)- Sheethal appears in both tables twice so wefind two matching pairs for her and hence tworows appears in the results.
  • Except• I want everyone on the clients list EXCEPT those onthe VIP list.• select * from clients except select * from vips;name----------------SharanVineeshBala
  • Except All• Lets insert a Sheethal(duplicate name) into clients.name----------------SharanVineeshBalaSheethalSheethal(4 rows)-select * from clients except all select * from vips;
  • Except Allname----------------SharanVineeshBalaSheethal(4 rows)
  • Where Clause• select * from Clients_Year;name | Birth year------------------+------Sharan | 1976Vineesh | 1977Bala | 1978Ashwathy | 1983Reshmi | 199 3sheethal | 1996Anupa | 1997
  • Where Clause• select * from clients_year where yearbetween 1970 and 1979 union select * fromceos where year=1977;name | Birth year------------------+------Sharan | 1976Vineesh | 1977Bala | 1978
  • Do not• select * from clients where year between1970 and 1979 union select name from clientswhere year=1977;ERROR: each UNION query must have thesame number of columns
  • Union and intersection in Python
  • Example>>>engineers = Set([John, Jane, Jack,Janice])>>>programmers = Set([Jack, Sam, Susan,Janice])>>>managers = Set([Jane, Jack, Susan,Zack])
  • Union>>>employees = engineers | programmers |managers>>>print “employees”Set([Jane, Janice, John’,Jack’,’susan’,’Zack’,’sam’])
  • Intersection>>>engineers = Set([John, Jane, Jack,Janice])>>>managers = Set([Jane, Jack, Susan,Zack])>>>engineering_management = engineers &managers>>>print “engineering_management”Set([Jane, Jack’])
  • Questions
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