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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;
Use Serially Reusable Packages To help you to manage the use of memory, the PL/SQL gives the pragma SERIALLY_ REUSABLE that mark some packages as serially reusable . So mark
Deleting Objects You can use the DELETE statement to eradicate objects from an object table. To eradicate objects selectively, you use the WHERE clause, as shown below: BEG
BETWEEN Operator The operator BETWEEN, tests whether the value lies in a specified series. That means "greater than or equivalent to low value and less than or equivalent to hig
Explicitly specifying the join condition - SQL SELECT * FROM IS_CALLED JOIN IS_ENROLLED_ON ON ( IS_CALLED.StudentId = IS_ENROLLED_ON.StudentId ) Now, the key word JO
Use of COUNT in SQL It describes and discusses various general methods of expressing constraints, eventually noting that support for "=" with relation operands is sufficient f
THEO R Y OF CATASTROPHISM OR CATALYSM (CUVIER 1769-1832) - The world has passed thorugh several stages and at the end of each stage there was a catastrophe killing all the
What are the rates for help in writing PL/SQL procedures and functions?
Consider the following set of database tables (same tables from Assignment 6-1). Please take note of foreign keys (most of them carry the same names as the corresponding primary ke
Use the MASCOT tables CREDITRS, PORDS and PAYMENTS to write SQL queries to solve the following business problems. These tables / data are available to you via the USQ Oracle server
Definition of CROSS JOIN - SQL Let s = t1 CROSS JOIN t2, where t1 and t2 are table expressions optionally accompanied by range variables. Then: Note: Here T denotes Table
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