marp
true

CheatSheet

Relation

SELECT * FROM Customers;
- cat Customer_A.csv
- awk '{print}' Customer_A.csv

Projektion

SELECT CustomerName, City FROM Customers;
- awk '{print $1}' Customer_A.csv
- awk -F ',' '{print $1}' Customer_A.csv
- awk -F ',' 'OFS = "," {print $3, $5}' Customer_A.csv
Bonus: Sortierung
- awk -F ',' 'OFS="," {print $2, $1, $3}' Customer_A.csv | sort --field-separator=',' --key=2

Selection

SELECT * FROM Customers WHERE Country LIKE '%ada%';
- cat Customer_A.csv | grep ada
- awk -F ',' 'OFS="," {if ($7 ~ /ada/) print $0}' Customer_A.csv

Vereinigung

SELECT * FROM Customers_A UNION SELECT * FROM Customers_B;
- cat Customer_A.csv Customer_B.csv
- cat Customer_A.csv Customer_B.csv | sort | uniq

Differenz

SELECT * FROM Customers_A EXCEPT SELECT * FROM Customers_B;
- comm -23 <(sort Customer_A.csv) <(sort Customer_B.csv)

Umbenennung

awk -F ',' 'OFS = "," {print $5, $3}' Customer_A.csv

Kartesisches Produkt

SELECT * FROM R, S;
- siehe: ./bin/crt.sh