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Aggregate AssignmentThe %ROWTYPE declaration cannot include an initialization clause. Though, there are two ways to assign values to all fields in a record at once. At First, the PL/SQL allows the aggregate assignment between the whole records if their declarations refer to the similar table or cursor. For illustration, the assignment below is legal:DECLAREdept_rec1 dept%ROWTYPE;dept_rec2 dept%ROWTYPE;CURSOR c1 IS SELECT deptno, dname, loc FROM dept;dept_rec3 c1%ROWTYPE;BEGIN...dept_rec1 := dept_rec2;However, because dept_rec2 is based on a table and dept_rec3 is based on acursor, the following assignment is illegal:dept_rec2 := dept_rec3; -- illegalSecondly, you can assign a list of column values to a record by using the SELECT or FETCH statement, as the illustration below shows. The column names should appear in the order in which they are defined by the CREATE TABLE or CREATE VIEW statement.DECLAREdept_rec dept%ROWTYPE;...BEGINSELECT deptno, dname, loc INTO dept_rec FROM deptWHERE deptno = 30;
Closing a Cursor Variable The CLOSE statement disables the cursor variable. After that, the related result set is undefined. The syntax for the same is as shown below: CLOS
Example of Foreign Key Constraint Example: Alternative formulation for 6.3 as a foreign key constraint ALTER TABLE EXAM_MARK ADD CONSTRAINT Must_be_enrolled_to_take_exam
Providing Results of Queries Expressing queries in SQL is the (big) subject. Here I present just a simple example to give you the flavour of things to come in those chapters.
Authorisations - Privileges As relational theory is silent on the issue of authorisation, it offers nothing with which SQL's vast edifice in support of what it calls privilege
Example of Null operator - NiNo Rule If we wanted to make HIGHER_OF adhere to "NULL in, NULL out"-let's call it the NiNo rule-we would have to write something like what is sho
Rephrase Conditional Control Statements When computing a logical expression, the PL/SQL uses short-circuit evaluation. That is, the PL/SQL stops evaluating the expression as s
Varrays versus Nested Tables The Nested tables are differing from varrays in the following ways: 1) Varrays have a maximum size, while nested tables do not. 2) Varrays are
SELECT a.child_fname,a.child_lname,concat(b.parent_title,b.parent_fname), b.parent_lname,b.parent_tphone FROM child a,parent b WHERE a.parent_id=b.parent_id ORDER BY a.child_fnam
Avoiding Collection Exceptions In many cases, if you reference a nonexistent collection element, then PL/SQL raises a predefined exception. Consider the illustration shown b
Updating Variables For assignment, SQL uses the key word SET, as in SET X = X + 1 (read as "set X equal to X+1") rather than X: = X + 1 as found in many computer languages.
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