55 lines
1.1 KiB
Markdown
55 lines
1.1 KiB
Markdown
![[sql_merged.pdf]]
|
|
|
|
|
|
SQL Tabellen sind multimengen von tupeln
|
|
Duplikate möglich!!!
|
|
|
|
## SQL Data Definition Language DDL
|
|
1. CREATE TABLE: zum Erstellen einer neuen Tabelle
|
|
2. ALTER TABLE: zum Ändern einer bestehenden Tabelle
|
|
3. DROP TABLE: zum Löschen einer Tabelle
|
|
[[DDL Data Definition Language SQL]]
|
|
|
|
## SQL Data Manipulation Language DML
|
|
1. INSERT
|
|
2. UPDATE
|
|
3. DELETE
|
|
|
|
[[DML Data Manipulation Language SQL]]
|
|
|
|
|
|
| SQL | Argumente | Relationale Algebra |
|
|
| ---------- | ------------------ | ------------------- |
|
|
| **SELECT** | Liste von Namen | $\pi$ |
|
|
| **FROM** | Liste von Tabellen | $\times$ |
|
|
| **WHERE** | Bedingung | $\sigma$ |
|
|
|
|
|
|
|
|
### SELECT
|
|
```
|
|
SELECT MatrNr, Name, Semester from Student
|
|
```
|
|
|
|
Spalte umbenennen
|
|
`SELECT MatrNr AS InsassenNr from Student`
|
|
|
|
Keine Duplikate
|
|
`SELECT DISTINCT Semester AS Jahrgänge from Student`
|
|
|
|
### WHERE
|
|
|
|
```
|
|
SELECT * from Student WHERE Semester = 2
|
|
---
|
|
SELECT * from Student s WHERE s.Semester = 2 AND s.Name='Byleth'
|
|
```
|
|
|
|
#### Anatomie einer WHERE Klausel
|
|
Vergleichsoperatoren: <,>,=,<=,>=,<>
|
|
BETWEEN
|
|
LIKE
|
|
IS NULL
|
|
AND, OR, NOT
|
|
|