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SQL Tutorial for Beginners
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SQL Tutorial for Beginners

SQL Tutorial for Beginners

1. Database & Introduction to Syntax
Meet the SQLSelect the Songs!SQL Select ColumnSQL DistinctSQL WhereChallenge WhereSQL And, Or, Not
2. SQL Aggregate Functions
SQL Min and MaxChallenge Min and MaxSQL Count, Sum, AvgChallenge Count
3. Filtering Statements
SQL NullSQL LikeChallenge LikeSQL BetweenSQL Order ByChallenge Order BySQL Group ByChallenge Group BySQL Top and LimitSQL AliasesSQL HavingChallenge HavingSQL Comments

book
SQL Group By

GROUP BY is an operator that puts rows with the same values of the field in groups. It creates one row for each group, so it makes sense to use some aggregate function in SELECT. For example, let's group our songs by singers, and find a number of songs for each singer:


              
123

            
SELECT COUNT(Id), singer
FROM songs
GROUP BY singer
copy

This query will return a list of singers, as well as, for each of them, the number of songs. Each singer represents a unit or group, and COUNT() aggregate function is applied for records in the group. You can use GROUP BY with ORDER BY, and also group by multiple columns. Here is a syntax of query:


              
123456

            
-- do not run this query
SELECT col1, col2, ...
FROM table
WHERE condition
GROUP BY col1, col2, ...
ORDER BY col1, col2, ...;
copy
Opgave

Swipe to start coding

For each singer, create groups with info about singer and price of the most expensive song. Order these groups by singer.

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 3. Kapitel 7
toggle bottom row

book
SQL Group By

GROUP BY is an operator that puts rows with the same values of the field in groups. It creates one row for each group, so it makes sense to use some aggregate function in SELECT. For example, let's group our songs by singers, and find a number of songs for each singer:


              
123

            
SELECT COUNT(Id), singer
FROM songs
GROUP BY singer
copy

This query will return a list of singers, as well as, for each of them, the number of songs. Each singer represents a unit or group, and COUNT() aggregate function is applied for records in the group. You can use GROUP BY with ORDER BY, and also group by multiple columns. Here is a syntax of query:


              
123456

            
-- do not run this query
SELECT col1, col2, ...
FROM table
WHERE condition
GROUP BY col1, col2, ...
ORDER BY col1, col2, ...;
copy
Opgave

Swipe to start coding

For each singer, create groups with info about singer and price of the most expensive song. Order these groups by singer.

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 3. Kapitel 7
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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