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Manipulating Individual ElementsFaraway you have manipulated an entire collection. Within the SQL, to manipulate the individual elements of the collection, and then use the operator TABLE. The operand of TABLE is a subquery which returns a single column value for you to manipulate. That the value is the nested table or the varray.In the illustration below, you add a row to the History Department nested table stored in the column courses:BEGININSERT INTOTABLE(SELECT courses FROM department WHERE name = ’History’)VALUES(3340, ’Modern China’, 4);END;In the next illustration, you revise the number of credits for two courses offered by the Psychology Department:DECLAREadjustment INTEGER DEFAULT 1;BEGINUPDATE TABLE(SELECT courses FROM departmentWHERE name = ’Psychology’)SET credits = credits + adjustmentWHERE course_no IN (2200, 3540);END;In the following illustration, you retrieve the number and the title of a specific course offered by the History Department:DECLAREmy_course_no NUMBER(4);my_title VARCHAR2(35);BEGINSELECT course_no, title INTO my_course_no, my_titleFROM TABLE(SELECT courses FROM departmentWHERE name = ’History’)WHERE course_no = 3105;...END;In the next illustration, you delete all 5-credit courses offered by the English Department:BEGINDELETE TABLE(SELECT courses FROM departmentWHERE name = ’English’)WHERE credits = 5;END;In the following illustration, you recover the title and cost of the Maintenance Department’s fourth project from the varray column projects:DECLAREmy_cost NUMBER(7,2);my_title VARCHAR2(35);BEGINSELECT cost, title INTO my_cost, my_titleFROM TABLE(SELECT projects FROM departmentWHERE dept_id = 50)WHERE project_no = 4;...END;Presently, you cannot reference the individual elements of a varray in an UPDATE, INSERT, or DELETE statement. And hence, you should use the PL/SQL procedural statements. In the illustration below, the stored procedure add_project inserts a new project into the department’s project list at a given position a shown:CREATE PROCEDURE add_project (dept_no IN NUMBER,new_project IN Project,position IN NUMBER) ASmy_projects ProjectList;BEGINSELECT projects INTO my_projects FROM departmentWHERE dept_no = dept_id FOR UPDATE OF projects;my_projects.EXTEND; -- make room for new project/* Move varray elements forward. */FOR i IN REVERSE position..my_projects.LAST - 1 LOOPmy_projects(i + 1) := my_projects(i);END LOOP;my_projects(position) := new_project; -- add new projectUPDATE department SET projects = my_projectsWHERE dept_no = dept_id;END add_project;The stored procedure updates below for a given project is:CREATE PROCEDURE update_project (dept_no IN NUMBER,proj_no IN NUMBER,new_title IN VARCHAR2 DEFAULT NULL,new_cost IN NUMBER DEFAULT NULL) ASmy_projects ProjectList;BEGINSELECT projects INTO my_projects FROM departmentWHERE dept_no = dept_id FOR UPDATE OF projects;/* Find project, update it, then exit loop immediately. */FOR i IN my_projects.FIRST..my_projects.LAST LOOPIF my_projects(i).project_no = proj_no THENIF new_title IS NOT NULL THENmy_projects(i).title := new_title;END IF;IF new_cost IS NOT NULL THENmy_projects(i).cost := new_cost;END IF;EXIT;END IF;END LOOP;UPDATE department SET projects = my_projectsWHERE dept_no = dept_id;END update_project;
Fetching from a Cursor Variable The FETCH statement retrieve rows one at a time from the product set of a multi-row query. The syntax for the same is as shown: FETCH {curso
Functions The function is a subprogram which can take parameters and be invoked. Normally, you can use a function to calculate a value. The function has 2 sections: the specifi
Write a program to implement the inverted file shown in the slides (Simple Index file, LabelID file and Data file). Use the Avail_List to point at the deleted Label IDs so that th
Parameter and Keyword Description: select_item: This select_item is a value returned by the SELECT statement, and then assigned to the equivalent variable or field in the
Error Handling The PL/SQL makes it easy to detect and process the predefined and user-defined error conditions known as exceptions. Whenever an error occurs, an exception is ra
Using Aliases The Select-list items fetched from a cursor related with the %ROWTYPE should have simple names or, if they are expressions, should have aliases. In the example bel
Data Abstraction The Data abstraction extracts the important properties of data while ignoring the not necessary details. Once you design a data structure, you can fail to reme
Many of the reports generated from the system calculate the total dollars in a shopper''s purchases. Follow these steps to create a function named TOT_PURCH_SF that accepts a shopp
Product-specific Packages The Oracle and different Oracle tools are supplied with the product-specific packages which help you to build the PL/SQL-based applications. For illus
Data Types in SQL - XML, Array, Row BINARY LARGE OBJECT for arbitrarily large bit strings. XML for XML documents and fragments. ARRAY types for arrays.
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