PL/SQL Function

PL/SQL Function is same as PL/SQL Procedure, The only difference is that function must return a value and a procedure may or may not return a value

PL/SQL Procedure

Previously I have posted about PL/SQL Block structure , A piece of code that is organized in a properly defined sequence is called a block

PL/SQL provides two types of blocks

Function- A PL/SQL block that performs a task or set of tasks and returns a value

Procedure- A PL/SQL block that performs a task or set of tasks and may or may not return a value

PL/SQL Exceptions

An error that occurs during execution of the program is called exception, Like other programming languages, PL/SQL offers a way to catch these exceptions and handle them.

There are two types of exceptions in PL/SQL

1. System-Defined Exceptions 
2. User-Defined Exceptions 

PL/SQL For Loop

PL/SQL FOR loop is used when we need to execute set of statements for the specific number of times and loop operates between the start and end counter values. The counter is always incremented by one and once the counter reaches to end integer value, the loop terminates

The syntax of PL/SQL FOR Loop is like this

FOR counter_variable IN start value.. end value LOOP

statements to execute 

END LOOP;

PL/SQL While Loop

PL/SQL WHILE loop is used to execute statements as long as given condition is true and the condition is checked at the beginning of each iteration

The syntax of PL/SQL While loop is like this

WHILE condition

statements to execute

END LOOP;

PL/SQL Loops , Iterative Statement in PL/SQL

Loops are used to repeat execution of a statement or a set of statements multiple times on base of a condition or expression
EXIT and EXIT-WHEN keywords are used to terminate the loop

EXIT- terminates the loop unconditionally and passes control to the next statement after the loop
EXIT-WHEN- terminates the loop when EXIT-WHEN clause is checked and if returns true then the loop is terminated and control is passed to next statement after the loop

The basic syntax of Loop in PL/SQL is like this

LOOP

Set of statements

END LOOP;

PL/SQL CASE Statement, Decision Making Statement in PL/SQL

Like real life in programming sometimes we need to execute some code on a specific condition, PL/SQL CASE statement allows us to execute a sequence of instructions based on a selector (A variable, function, expression etc)
and if selector value is equal to value or expression in WHEN clause then corresponding THEN clause will execute and process the statements

PL/SQL Conditions, IF-ELSE Conditional Statement

Like other programming languages, PL/SQL supports decision making statements, These statements are also called conditional statement

Basic Syntax of IF-ELSE is like this in PL/SQL

IF (Condition 1)

THEN

Statement to execute (if condition 1 is true)

ELSIF (Condition 2)

THEN 

Statement to execute (if condition 2 is true)

ELSE

Statement to execute (if condition 1& 2 both are false)

END IF;

For a better understanding of concept look at these examples

PL/SQL Variables and Constants

A variable in any programming language is the name of space where values are stored and controlled by our code/program

• We can not use reserve keyword as a variable name 
• Variable length should not exceed 30 characters
• The variable name consists of letters followed by other letters, dollar sign, underscore and numerals
• The variable name should be clear and easy to understand

Here we'll learn how to declare and initialize variables in PL/SQL

The basic syntax for declaring a variable in PL/SQL is following

variable_name [CONSTANT] datatype [NOT NULL] [:= | DEFAULT initial_value] 

Here variable_name is the identifier of variable and datatype is a valid PL/SQL datatype. CONSTANT and DEFAULT are keywords used to define constants and set default values of variables

PL/SQL Tutorial - What is PL/SQL, Features and Advantages of PL/SQL

PL/SQL is developed by Oracle Corporation to increase/enhance capabilities of SQL, PL/SQL stands for Procedural Language extension to SQL . PL/SQL is highly structured and expressive language and because of its expressive syntax it is very easy to understand and learn

PL/SQL is integrated with Oracle Database and can be called from any other programming language. It is tightly integrated with SQL so it's easy to learn PL/SQL if you have knowledge of SQL

Executing SQL query in an ADF Application using DBTransaction & JDBC DataSource

hello all,
this post is about executing SQL query in your ADF Application
Sometimes we need to execute some query in our managed bean or any of implementation class of Model, this is quite easy

• I have a fusion web application having connection with hr schema of Oracle DB
• now i have to get Max Department Id of Departments Table using this statement



SELECT max(DEPARTMENT_ID) CODE FROM DEPARTMENTS



• So to execute this query i have created a method in AMImpl class using DBTransaction



    /**Method to Execute DB SQL Query using DBTransaction
     * @param query
     * @return
     */
    protected Integer executeQuery(String query) {
        ResultSet rs;
        Integer code = null;
        try {
            rs = getDBTransaction().createStatement(0).executeQuery(query);
            if (rs.next()) {
                code = ((BigDecimal) rs.getObject(1)).intValue();
            }

            rs.close();
            return code;

        } catch (SQLException e) {
            throw new JboException(e);
        }
    }



• now called this method and passed my SQL statement





        Integer deptID = executeQuery("SELECT max(DEPARTMENT_ID) CODE FROM DEPARTMENTS");
        System.out.println("Department Id-" + deptID);


And Output is-



• Second way is by using JDBC DataSource , for this first we have to get Connection using DataSource Name- see this method



    /**Method to get Connection using JDBC DataSource Name
     * @param dsName
     * @return
     * @throws NamingException
     * @throws SQLException
     */
    public static Connection getConnectionDS(String dsName) throws NamingException, SQLException {
        Connection con = null;
        DataSource datasource = null;

        Context initialContext = new InitialContext();
        if (initialContext == null) {
        }
        datasource = (DataSource) initialContext.lookup(dsName);
        if (datasource != null) {
            con = datasource.getConnection();
        } else {
            System.out.println("Failed to Find JDBC DataSource.");
        }
        return con;
    }



• Now after getting connection , we can execute SQL query using Statement or PreparedStatement
• Go to your ApplicationModule to get DataSource Name, in Configuration tab open AMLocal

•  Copy DataSource Name , and use it to get Connection and to execute query



        Connection con = null;
        try {
            con = getConnectionDS("java:comp/env/jdbc/APPDS");
        } catch (SQLException e) {
        } catch (NamingException e) {
        }
        try {
            PreparedStatement stmt = con.prepareStatement("SELECT * FROM DEPARTMENTS");
            ResultSet rs = stmt.executeQuery();
            while (rs.next()) {
                System.out.println("Department Id-" + rs.getInt(1) + " and Department Name-" + rs.getString(2));
            }

            rs.close();


        } catch (SQLException e) {
            throw new JboException(e);
        }



• After executing see the output- 

 Cheers :-) happy coding