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SQL Cheet Sheat
Data Definition Language
CREATE SCHEMA hollywood;CREATE TABLE hollywood.films (title text, release date, awardstext[]);
CREATE TABLE personen(ID INTEGER PRIMARY KEY,Name CHAR(30) NOT NULL,Abteilung VARCHAR(5),Telefonnummer TEXT, Postleitzahl NUMERIC,Name_des_Wohnorts CHAR(30),Jahr_der_Einstellung DATE REFERENCES Abteilung); //secondary Key
Data Manipulation Language
insert into Vorlesungen (VorlNr, Titel, SWS, gelesenVon)values (5099, `Methaphysik, 4, 2137);
insert into hrenselect MatrNr, VorlNrfrom Studenten, Vorlesungenwhere Titel= `Logik ;
update Studenten set Semester= Semester + 1;
delete
Data Query Language
select
select distinct ..
SELECT a, a*100/c AS percentage
SELECT a "given as an A"
COUNT(*)with wildcard counts every line or
COUNT(name)counts every filled line,
COUNT(distinct name)`
sort
select name from personen order by Rang desc,Name asc
Join
FROM (student s JOIN personen h ON (s.Matr_nr=h.Matr_nr and s.Name='Lovelace')
students JOIN lectures v USING Vorl_nr
students NATURAL JOIN lectures
students LEFT JOIN lectures
also students without a lecture are in table
UNION, INTERSECT, EXCEPT
find all: select name from assistent) union (select name from professors)
LIKE
wildcard "%" ; ""
"%" any amound
"" exactly one charwhere title like '%thik%';
notin, all, ect
ect: 'avg(age), max(age), min(age), count(*), sum(meter)`
where PersNr not in (select gelesenVon from Vorlesungen );
where Semester >= all ( select Semester from Studenten);
same as: where Semester >= ( select max(Semester) from Studenten);
`
group by
select gelesenVon, Name, avg(SWS)
from Vorlesungen, Professoren
where gelesenVon = PersNr
group by gelesenVon, Name
having avg(SWS) >= 3;
Query in FROM
FROM
(SELECT * FROM Studenten s JOIN hoeren h USING (Matr_nr)
WHERE s.Name='Lovelace') lovelace_hoert`
has to have a name
declutter querys
With alias_name1 as(select ...from... where...),alias_name2 as(select ...from... where...)'
select * from Studenten where Semester between 1 and 4;
select * from Studenten where Semester in (1,2,3,4);
select MatrNr, (case when Note<1.5 then sehr gutwhen Note<2.5 then gutwhen Note<3.5 then befriedigendwhen Note <= 4 then ausreichendelse Nicht bestanden end)from pruefen;
select s.MatrNr, s.Name, avg(Note) as persDurchschnitt,(select avg(note) as Gesamtsschnitt from pruefen p)from Studenten s, pruefen pwhere s.MatrNr=p.MatrNrgroup by s.MatrNr, Namehaving persDurchschnitt < select avg(note) from pruefen p
Original Link: https://dev.to/annequinkenstein/sql-cheet-sheat-57ga
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