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Data Manipulation using SQL
course content

Kursusindhold

Data Manipulation using SQL

Data Manipulation using SQL

1. Database and Nested Queries
DatabaseSQL In StatementChallenge In StatementSQL Exists Statement
2. SQL Joining Tables
SQL Inner JoinSQL JoinsSQL Left & Right JoinSQL Full Outer JoinSQL Union
3. SQL Tasks
Challenge: Albums with Two SongsChallenge: the Biggest AlbumChallenge: Rating of SingersChallenge: DecadesChallenge: Two SingersChallenge: Solo vs BandsChallenge: Solo AlbumsChallenge: Singers Stats

book
SQL Union

UNION is an operator that concatenates results of different SQL queries:


              
1234567

            
--do not run this query
SELECT columns FROM table1
UNION
SELECT columns FROM table2
UNION
...
SELECT columns FROM tableN
copy

There is also an operator UNION ALL, and the difference is that UNION returns distinct values, unlike UNION ALL.

Requirements for using UNION operators:

  • number of columns in SELECT should be the same
  • data types and order of columns should be the same
Opgave

Swipe to start coding

You want to get some info about songs from three decades: 1970s, 1980s, and 1990s. Find the prices of the cheapest and the most expensive songs for each decade in separate queries. You're free to use JOIN, BETWEEN, or any other operators, but you should do three separate queries and concatenate them with UNION.

Løsning

Switch to desktopSkift til skrivebord for at øve i den virkelige verdenFortsæt der, hvor du er, med en af nedenstående muligheder
Var alt klart?

Hvordan kan vi forbedre det?

Tak for dine kommentarer!

Sektion 2. Kapitel 5
toggle bottom row

book
SQL Union

UNION is an operator that concatenates results of different SQL queries:


              
1234567

            
--do not run this query
SELECT columns FROM table1
UNION
SELECT columns FROM table2
UNION
...
SELECT columns FROM tableN
copy

There is also an operator UNION ALL, and the difference is that UNION returns distinct values, unlike UNION ALL.

Requirements for using UNION operators:

  • number of columns in SELECT should be the same
  • data types and order of columns should be the same
Opgave

Swipe to start coding

You want to get some info about songs from three decades: 1970s, 1980s, and 1990s. Find the prices of the cheapest and the most expensive songs for each decade in separate queries. You're free to use JOIN, BETWEEN, or any other operators, but you should do three separate queries and concatenate them with UNION.

Løsning

Switch to desktopSkift til skrivebord for at øve i den virkelige verdenFortsæt der, hvor du er, med en af nedenstående muligheder
Var alt klart?

Hvordan kan vi forbedre det?

Tak for dine kommentarer!

Sektion 2. Kapitel 5
Switch to desktopSkift til skrivebord for at øve i den virkelige verdenFortsæt der, hvor du er, med en af nedenstående muligheder
Vi beklager, at noget gik galt. Hvad skete der?
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