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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.)
Data Types in SQL - Timestamp TIMESTAMP for values representing points in time on a specified uniform scale. DATE is used for timestamps on a scale of one day, such as DATE '2
Using SET TRANSACTION You use the SET TRANSACTION statement to begin the read-only or read-write transaction, start an isolation level, or assign your present transaction to a
Datatypes Every constant and variable has a datatype that specifies the storage format, constraints, and the valid range of values. The PL/SQL gives a variety of predefined dat
Assigning and Comparing Collections One collection can be assigned to other by an SELECT, INSERT, UPDATE, or FETCH statement, an assignment statement, or by a subprogram call. A
Advantages of PL/SQL The PL/SQL is a high-performance transaction processing, completely portable language that offers the following advantages as shown: 1) Support for SQL
Mixed Notation The fourth procedure call shows that you can mix the positional and named notation. In this situation, the first parameter uses the positional notation, & the s
Autonomous versus Nested Transactions Though an autonomous transaction is started by the other transaction, it is not a nested transaction for the reasons shown below: (i)
Initializing and Referencing Collections Until you initialize a collection, a nested table or varray is automatically null (i.e. the collection itself is null, not its elements)
%ROWCOUNT The %ROWCOUNT yields the number of rows affected by the INSERT, UPDATE, or DELETE statement, or returned by a SELECT INTO statement. The %ROWCOUNT yields zero when a
Structure of an Object Type: Similar to package, an object type has 2 parts: the specification and the body. The specification is the interface to your applications; it declar
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