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Declarations in SQLYour program stores values in the variables and constants. As the program executes, the value of the variables can change, but the values constants cannot. You can declare the variables and constants in the declarative part of any PL/SQL block, package, or subprogram. The Declarations allocate the storage space for a value, state its datatype, and name the storage location and hence, you can reference it. A couple of examples are shown below: birthday DATE;emp_count SMALLINT := 0;The first declaration names a variable of the type DATE. The second declaration names a variable of the type SMALLINT and uses the assignment operator to assign an initial value of zero to the variable. The example next show that the expression following the assignment operator can be arbitrarily complex and can refer to the earlier initialized variables: pi REAL := 3.14159;radius REAL := 1;area REAL := pi * radius**2; By default, the variables are initialized to NULL. So, these declarations are equal: birthday DATE;birthday DATE := NULL; In the declaration of a constant, the keyword CONSTANT should precede the type of the specifier, as the example below shows: credit_limit CONSTANT REAL := 5000.00; This declaration names a constant of the type REAL and assigns an initial value of 5000 to the constant. The constant must be initialized in its declaration. Or else, you get a compilation error whenever the declaration is elaborated. (The procedure of a declaration by the PL/SQL compiler is known as the elaboration.)
UNION without CORRESPONDING - SQL The use of UNION without CORRESPONDING. Example is merely by omitting CORRESPONDING, but only because the operands have identical SELECT clau
Bulk Fetching The illustration below shows that you can bulk-fetch from a cursor into one or more collections: DECLARE TYPE NameTab IS TABLE OF emp.ename%TYPE; TYPE S
Forward Declarations The PL/SQL needs that you declare an identifier before using it. And hence, you should declare a subprogram before calling it. For illustration, the decla
Overloading: Similar to packaged subprograms, methods of the same type can be overloaded. That is, you can use similar name for various methods if their formal parameters diff
Example of GROUPBY Operator Example: How many students sat each exam, using GROUP BY, NATURAL LEFT JOIN, and COALESCE SELECT CourseId, COALESCE (n, 0) AS n FROM COURS
Transaction Visibility As the figure shows, the changes made by an autonomous transaction become visible to another transaction whenever the autonomous transaction commits. Th
Example of Shorthand for a row constraint Example: Shorthand for a row constraint ALTER TABLE EXAM_MARK ADD CONSTRAINT Mark_in_range CHECK (Mark BETWEEN 0 AND 100);
Using Savepoints The scope of the savepoint is a transaction in which it is defined. The Savepoints defined in the major transaction are not related to the savepoints defined
Mutual Recursion The Subprograms are mutually recursive if they directly or indirectly call each other. In the illustration below, the Boolean functions odd & even, that dete
Oracle 11 G new features associated with this release:- Enhanced ILM - Information Lifecycle Management (ILM) has been around for the almost 10 years, but Oracle has made
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