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UsingPLSQLWithOracleServer - Block statements Learning...

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Block statements Learning objective After completing this topic, you should be able to write lexical units in their correct format in a PL/SQL block. 1. Identifiers A block is the most basic unit of code in the PL/SQL programming language. You use a series of blocks to build a module, such as a procedure or a function. A collection of modules makes up an application. Lexical units are the elements that make up each PL/SQL block. You use sequences of letters, numbers, special characters, symbols, spaces, tabs, and returns to create the various lexical units. Each lexical unit can be classified as an identifier a delimiter a literal a comment Identifiers are used to give names to variables. An identifier can be any of the following PL/SQL objects: a constant an exception a function a package a procedure For example, here you are naming a date variable, " begin date" , and assigning a value to the variable. The identifier is begin_date . DECLARE begin_date DATE:= '20-Mar-2001'; An identifier can be a maximum of 30 characters in length must start with a letter can contain $ (dollar sign), # (pound sign), and _ (underscore) characters cannot contain blank spaces, unless it is a quoted identifier Here's an example of a PL/SQL block using a number of identifiers to define variables. In the first declaration section, you have identified the output for Father's Name as a variable, father_name , which in this case is Patrick .
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The second variable identifies 20-Apr-1972 as the value of date_of_birth . SET SERVEROUTPUT ON DECLARE father_name VARCHAR2(20):='Patrick'; date_of_birth DATE:='20-Apr-1972'; BEGIN DECLARE child_name VARCHAR2(20):='Mike'; date_of_birth DATE:='12-Dec-2002'; BEGIN DBMS_OUTPUT.PUT_LINE('Father''s Name: '||father_name); DBMS_OUTPUT.PUT_LINE('Date of Birth: '||date_of_birth); DBMS_OUTPUT.PUT_LINE('Child''s Name: '||child_name); END; DBMS_OUTPUT.PUT_LINE('Date of Birth: '||date_of_birth); END; / You then use these identifiers to specify how the output will appear. And here is the output after using the identifiers. You can get around some of the restrictions of identifiers by placing the quote marks around the identifier, as shown here. Using quote marks enables you to make identifiers case sensitive include characters such as spaces use reserved words make identifiers case sensitiveinclude characters such as spacesuse reserved words DECLARE "Begin Date" DATE:= '20-Mar-2001'; Question You are writing PL/SQL to output the names of an employee. You want to name the First Name variable first name , and assign it the value Carol . Complete the missing code to use an identifier to retrieve this first name. SET SERVEROUTPUT ON DECLARE MISSING CODE VARCHAR2(20):='Carol' Answer You enter "first name" to use an identifier to retrieve the First Name, Carol.
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2. Literals A literal is any value, such as a character, number, or Boolean statement, that is not an identifier. There are four types of literals: character literals numeric literals Boolean literals Datetime literals character literals
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