內部的 SELECT 查詢稱為子查詢,而外部的 SELECT 查詢即稱為主查詢 (main query)。 子查詢用法 (Example) 我們現在利用子查詢來達到跟MINUS相同的查詢結果。 這是公司在台灣地區銷售的產品資料表 products_taiwan: P_IdP_Name 1LCD 2CPU 3RAM 這是公司在中國大陸地區銷售的產品資料表 products_china: ...
In eine SELECT-Anweisung kann eine zweite SELECT-Anweisung ( Subquery (subquery)) eingeschlossen werden. Durch die Subquery wird ein Wert oder eine Menge von Werten als Teil der Hauptanweisung erzeugt.VoraussetzungenSie benötigen die Demo-Daten für das SQL-Tutorial....
SQL Tutorial, Subquery: Inner QueriesExplanationSubqueries can be used in a SET UPDATE clause of an UPDATE statement. In this case, the subquery must produce a result table that contains a maximum of one row.Subqueries can be used in an INSERT statement (INSERT statement)....
In this example, we used a subquery in theSELECTclause to get the average product’s list price. Oracle evaluates the subquery for each row selected by the outer query. This subquery is called acorrelated subquerywhich we will cover in detail in thenext tutorial. Oracle subquery in the FROM...
InSQL, efficient data retrieval is paramount in building dynamic, scalable applications. As databases grow more complex, the ability to filter, manipulate, and access data effectively becomes important. In this tutorial, we’ll explore two powerful tools for data handling and retrieval, subqueries an...
SQL Subquery Example: 1) Usually, a subquery should return only one record, but sometimes it can also return multiple records when used with operatorsLIKE IN, NOT IN in the where clause. The query syntax would be like, SELECT first_name, last_name, subject ...
There are several different ways to use subqueries inUPDATE statements. Let’s take a look at each of them. SET and Subquery The first method we will look at is using a subquery in the SET clause of an UPDATE statement. Let’s say we had a table of products that looked like this: ...
Summary: in this tutorial, you will learn about the Oracle correlated subquery which is a subquery whose some clauses refer to the column expressions in the outer query. Introduction to the Oracle correlated subquery# A correlated subquery is asubquerythat references columns from its outer query....
Egal, ob du ein Anfänger oder ein erfahrener Profi bist, die Beherrschung von Unterabfragen kann deine SQL-Kenntnisse erheblich verbessern. Wenn du neu in SQL bist, solltest du mit unserem SQL-Kurs für Fortgeschrittene beginnen, um eine solide Grundlage zu schaffen. Außerdem finde...
SQL Tutorial - W3Schools The SQL Tutorial for Data Analysis | SQL Tutorial - Mode Analytics Understanding Relational Tables The key here is thathaving multiple occurrences of the same data is never a good thing, and that principle is the basis for relational database design. Relational tables ar...