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--- modul:m290:learningunits:lu02:theorie:d_sql [2024/08/13 11:40] – angelegt vdemir
+++ modul:m290:learningunits:lu02:theorie:d_sql [2024/10/02 15:10] (aktuell) – vdemir
@@ Zeile 1: / Zeile 1: @@
-===== LU02c
+====== LU03c - SQL and its sub-types ======
-dadfasdf
+===== SQL and its sub-types =====
+**SQL** (Structured Query Language) is a standard language for managing and manipulating relational databases. It provides a set of commands for defining, querying, manipulating, and controlling data.
+In detail, SQL consists of five sub-languages, each of which is responsible for a specific group of operations. Please note that only the subtypes in bold are relevant for module 290.
+  * **DDL = Data Definition Language**: DDL commands are used to create, modify, and delete database structures, e.g. to create database instances and tables, to alter table structures or or to ftop databases and tables.
+  * **DQL = Data Query Language**: DQL commands are used to retrieve data from the database, e.g. to select table contents with and without filters and in a specific order.
+  * TCL = Transaction Control Language: The SQL subtype Transaction Control Language (TCL) manages transactions within a database, allowing you to commit, rollback, or set savepoints to ensure data integrity.
+  * **DML = Data Manipulation Language**: DML commands are used to insert, update and delete data in tables. DML commands are therefore used to manage table content: to insert new content or to update and delete using certain filters.
+  * **DCL = Data Control Language**: DCL commands are used to control access to the database. This includes the management of authorisations and the administration of user profiles. The central questions here are: "Which user is allowed to access which database object?"
+{{:modul:m290:learningunits:lu02:theorie:sql_uebersicht.jpg?800|}}
+===== Correlation of SQL and CRUD =====
+CRUD operations is to be applied in all three layers of a three-layers-web-architecure (presentation layer, logic layer/server, data layer). Within the data layer the CRUD operations are realised as follows:
+{{:modul:m290:learningunits:lu02:theorie:crud_sql.jpg?600|}}
+===== Vocabulary =====
+^ English ^ German ^
+| to provide | bereitstellen |
+| to querty | (an-)fragen |
+| to consists of | bestehen aus |
+| instance | Exemplar, Komponente |
+| to alter | verändern |
+| therefore | daher |
+| to access | zugreifen |
+| to be allowed to | darf |
+----
+{{tag>M290-LU02}}
+[[https://creativecommons.org/licenses/by-nc-sa/4.0/|{{https://i.creativecommons.org/l/by-nc-sa/4.0/88x31.png}}]] Volkan Demir