Zwischenstand

daten-abfragen/notes.md

@@ -1,10 +1,17 @@
 # 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.
+3. Wenn auf distinct mehrere Spalten folgen, dann wird die Kombination der Spalten als einzigartig betrachtet.
+4. `WHERE firstname = 'Anne' OR firstname = 'Peter'` kann durch `WHERE firstname IN ('Anne', 'Peter')` ersetzt werden.
+5. `WHERE age BETWEEN 20 AND 30` gibt alle Werte zurück, wo das Alter zwischen 20 und 30 liegt.
 
 # Syntax
 `SELECT COUNT(*)` Zählt die Anzahl der Zeilen in einer Tabelle.
 
-`SELECT DISTINCT ` Gibt nur einzigartige Werte zurück.
+`SELECT DISTINCT ` Gibt nur einzigartige Werte zurück.
+
+`SELECT * FROM table WHERE column LIKE 'a%'` Gibt alle Werte zurück, die mit 'a' beginnen.
+
+`SELECT * FROM table WHERE age BETWEEN 20 AND 30` Gibt alle Werte zurück, wo das Alter zwischen 20 und 30 liegt. (Inklusive 20 und 30)
+

daten-abfragen/select-basic-2.sql

@@ -0,0 +1,99 @@
+select *
+from customers
+where email like '%@gmail.com';
+select *
+from customers
+where email like '%@web.de';
+select *
+from customers
+where email like '%@web.de'
+   or email like '%@gmail.com';
+
+select distinct SUBSTRING_INDEX(email, '@', -1) as domain
+from customers;
+# Nicht im Kurs, aber aus Interesse ausprobiert ---> Selektiert alle verschiedenen E-Mail Domains
+
+select *
+from customers
+where firstname like 'M%';
+select *
+from customers
+where firstname like 'M_____';
+
+select firstname, lastname, age
+from customers
+where age between 20 and 30;
+
+select *
+from customers
+where age not between 20 and 30;
+
+select *
+from customers
+where firstname in ('Gitta', 'Dana', 'Anne');
+
+select count(*)
+from customers
+where age not between 20 and 30; # 160
+
+select count(distinct baby_names.name)
+from baby_names
+where name like 'Alex%'; # 20
+select distinct baby_names.name
+from baby_names
+where name like 'Alex%';
+
+select distinct baby_names.name
+from baby_names
+where name like '%m%';
+select count(distinct baby_names.name)
+from baby_names
+where name like '%m%'; # 1183
+
+select *
+from baby_names
+where year between 1900 and 1999;
+select count(*)
+from baby_names
+where year between 1900 and 1999; # 161668
+select count(*)
+from baby_names
+where year >= 1900
+  and year <= 1999; # 161668
+
+select *
+from baby_names
+where year = 1900
+   or year = 1910
+   or year = 1920
+   or year = 1930
+   or year = 1940
+   or year = 1950
+   or year = 1960
+   or year = 1970
+   or year = 1980
+   or year = 1990;
+select count(*)
+from baby_names
+where year = 1900
+   or year = 1910
+   or year = 1920
+   or year = 1930
+   or year = 1940
+   or year = 1950
+   or year = 1960
+   or year = 1970
+   or year = 1980
+   or year = 1990; # 15307
+select count(*)
+from baby_names
+where year in (1900, 1910, 1920, 1930, 1940, 1950, 1960, 1970, 1980, 1990); # 15307
+
+select count(*)
+from baby_names
+where year like '19%0'; # 15307
+
+select count(*)
+from baby_names
+where year % 10 = 0
+  and year between 1900 and 1999; # 15307

daten-abfragen/select-basic.sql

@@ -50,6 +50,12 @@ select count(*)
 from baby_names
 where gender = 'm'; # 94322
 
+select `count`
+from baby_names
+where name = 'Alex'
+  and year = 2010
+  and gender = 'm';
+
 select count(distinct baby_names.name)
 from baby_names; # 6809
 
@@ -64,4 +70,13 @@ select *
 from baby_names
 where `count` = 19250; # Sandra
 
-select * from baby_names where gender != 'm' and gender != 'f';
+select *
+from baby_names
+where gender != 'm'
+  and gender != 'f';
+
+select distinct baby_names.gender
+from baby_names; # M, F
+
+select count(distinct baby_names.name, baby_names.gender)
+from baby_names;