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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;
Write SQL queries to solve the following specifications. Include the query AND THE OUTPUT. A screen dump of the output is acceptable. Show as many rows as you can. A screen dump i
Question: (a) The objective of query optimization is to choose the most efficient strategy for implementing a given relational query, thereby improving the system performance. On
DELETE Command - SQL Loosely speaking, DELETE removes some existing rows from its target table. Suppose the university decides that course C3 is to be withdrawn. Example shows
How Calls Are Resolved? The figure shows that how the PL/SQL compiler resolves the subprogram calls. When the compiler encounters the procedure or function call, it tries to di
UPDATE Command- SQL Loosely speaking, UPDATE changes some of the column values of some existing rows of its target table. Thus, although some rows disappear from the target an
What Is a Record ? A record is a group of related data items that stored in the fields, each with its own name and datatype. Assume that you have different data about an em
Naming Conventions The similar naming conventions apply to all PL/SQL program items and units including the variables, cursors, constants, cursor variables, procedures, exception
Redeclaring Predefined Exceptions Keep in mind that, the PL/SQL declares predefined exceptions globally in the package STANDARD; Therefore you need not declare them yourself.
LOOP Statements The LOOP statements execute a series of statements at multiple times. The loops enclose the series of statements that is to be repeated. The PL/SQL provides typ
Declaring and Initializing Objects: An object type is once defined and installed in the schema; you can use it to declare the objects in any PL/SQL, subprogram, block or packa
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