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--- modul:m290:learningunits:lu04:theorie:a_syntax [2024/08/30 09:47] – vdemir
+++ modul:m290:learningunits:lu04:theorie:a_syntax [2024/10/17 12:33] (aktuell) – vdemir
@@ Zeile 1: / Zeile 1: @@
-====== LU04a - Syntax of DML ======
+====== LU06a - Syntax of a DQL-Select statement ======
-===== Introduction =====
+As we know, **SQL** stands for **S**tructured **Q**uery **L**anguage. Consequently, It should come as no surprise that SQL is indeed consistently structured. The figure below shows the  structure of a exhaustive SQL statement.
-As we know, **SQL** stands for **S**tructured **Q**uery **L**anguage. Consequently, It should come as no surprise that SQL is indeed consistently structured.
+{{:modul:m290:learningunits:lu04:theorie:sql-syntax.png?600|}}
+===== NOTES  =====
+  * The content of this chapter is based on the  [[https://www.w3schools.com/sql/sql_syntax.asp|W3School-SQL-tutorial]].
+  * Please note that the use og CAPITAL LETTERS for SQL commands and tabs can make it easier for you to maintain your program code.
+  * Make sure, that every complete sql statement is finished by a semicolon (;).
 ===== The Syntax of DML commands =====
 Every SQL query is composed by three main commands:
-  * **SELECT**
-  * **FROM** and
-  * **WHERE** where.
-With SELECT you specify which columns you want to have output; with FROM you specify the TABLE from which the columns originate; and with WHERE you specify the condition under which the data records are selected. Where does not have to occur if there is no condition.
+  * **SELECT** myColumn1, myColumn2, ... [or * for all columns]
+  * **FROM** myTable
+  * **WHERE** myCondition.
+  * **ORDER BY** myColumn2 **ASC|DESC**;
+With **SELECT** we specify which columns we want to retrieve, with **FROM** we specify the TABLE from which the columns originate, with **WHERE** we determine the condition under which the data records are selected, and finally, with **ORDER BY** +  **[ASC | DESC]** we define the order in which the result set is to be displayed on the screen.
+===== Basic example =====
+Let's take a table **Customers** as shown in the figure below.
+{{:modul:m290:learningunits:lu04:theorie:screenshot_2024-08-30_095010.png?700|}}
+To retrieve all the information, which are stored in this table, our SQL command would be like follows.
+   SELECT *
+   FROM Customers;
+or as a more detailed notation
+   SELECT CustomerID, CustomerName, ContactName, Address, City, PostalCode, Country
+   FROM Customers;
+The result set would include the entire contents of the table, since we we have not defined any preconditions or filters.
-===== NOTE =====
-Please note that the use og CAPITAL LETTERS for SQL commands and tabs can make it easier for you to maintain your program code.
 ===== Vocabulary =====
 ^ English ^ German ^
+| precondition | Vorbedingung |
+| exhaustive  | erschöpfend, vollständig |
+| clause | Abschnitt |
+| to determine | bestimmen |
+| to fetch | abrufen, holen |
 | be composed by | besteht aus |
+| notation | Schreibweise |
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 [[https://creativecommons.org/licenses/by-nc-sa/4.0/|{{https://i.creativecommons.org/l/by-nc-sa/4.0/88x31.png}}]] Volkan Demir