Initial

daten-abfragen/notes.md

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+# Daten abfragen
+
+1. Bei Suche nach Daten, die Daten immer in `` ` `` Quotes setzen. Sonst werden die Spalten miteinander verglichen.
+
+2. MySQL ignoriert Groß- und Kleinschreibung und Ä = A, Ö = O, Ü = U.
+
+# Syntax
+`SELECT COUNT(*)` Zählt die Anzahl der Zeilen in einer Tabelle.
+
+`SELECT DISTINCT ` Gibt nur einzigartige Werte zurück.

daten-abfragen/select.sql

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+# use bookstore;
+
+select *
+from customers;
+
+select customers.firstname, customers.lastname, customers.age
+from customers;
+
+select count(*)
+from customers
+where customers.age > 30;
+
+select count(*)
+from customers
+where customers.age > 30
+  AND customers.age < 40;
+
+select *
+from customers
+where title = 'Frau Dr.'
+   OR title = 'Herr Dr.';
+
+select *
+from customers
+where (title = 'Frau Dr.' OR title = 'Herr Dr.')
+  AND age < 30;
+
+select count(distinct customers.lastname)
+from customers;
+
+select count(customers.age)
+from customers
+where age < 30;
+
+select distinct customers.firstname
+from customers;
+
+select distinct customers.firstname, lastname
+from customers;
+
+select count(distinct customers.firstname)
+from customers;
+
+# Aufgabe SELECT
+
+select count(*)
+from baby_names; # 220636
+
+select count(*)
+from baby_names
+where gender = 'm'; # 94322
+
+select count(distinct baby_names.name)
+from baby_names; # 6809
+
+select count(distinct baby_names.name)
+from baby_names
+where gender = 'm'; # 2756
+select count(distinct baby_names.name)
+from baby_names
+where gender = 'f'; # 4535
+
+select *
+from baby_names
+where `count` = 19250; # Sandra
+
+select * from baby_names where gender != 'm' and gender != 'f';