Lexical Units: -A programming language has lexical units that are the building blocks of the language.
PL/SQL lexical units fall within one of the following five groups:
1) Identifiers must begin with a letter and may be up to 30 characters long.
2) Reserved words are words that PL/SQL saves for its own use (such as BEGIN, END, and SELECT).
3) Delimiters are characters that have special meaning to PL/SQL, such as arithmetic operators and quotation marks.
4) Literals are values (character, numeric, or Boolean [true/false]) that are not identifiers.
123, “Declaration of Independence,” and FALSE are examples of literals.
5) Comments can be either single-line comments (--) or multi-line comments (/* */).
Identifiers/Variables:- Variables are used to hold a temporary value. Variables must begin with a letter.
Example:-
v_student_id
v_last_name
V_LAST_NAME
apt_#
Substitution Variable:-SQL*Plus allows a PL/SQL block to receive input information with the help of substitution variables. Substitution variables cannot be used to output values, because no memory is allocated for them. SQL*Plus substitutes a variable before the PL/SQL block is sent to the database. Substitution variables usually are prefixed by the ampersand (&) or double ampersand (&&) characters.
Example:-
DECLARE
v_num number:=#
v_result number;
BEGIN
v_result := POWER(v_num, 2);
DBMS_OUTPUT.PUT_LINE ('The value of v_result is: '||v_result);
END;
/
Note:- Here "num" is the substitution variable.
Reserved Words:- These are the words that can not be used as a variable or literals.
Example:-
BEGIN,DECLARE,END,LOOP,CASE,SELECT,INTO,FROM
Example:- Smallest program in PLSQL
begin
null;
end;
/
1) Identifiers must begin with a letter and may be up to 30 characters long.
2) Reserved words are words that PL/SQL saves for its own use (such as BEGIN, END, and SELECT).
3) Delimiters are characters that have special meaning to PL/SQL, such as arithmetic operators and quotation marks.
4) Literals are values (character, numeric, or Boolean [true/false]) that are not identifiers.
123, “Declaration of Independence,” and FALSE are examples of literals.
5) Comments can be either single-line comments (--) or multi-line comments (/* */).
Identifiers/Variables:- Variables are used to hold a temporary value. Variables must begin with a letter.
Example:-
v_student_id
v_last_name
V_LAST_NAME
apt_#
Substitution Variable:-SQL*Plus allows a PL/SQL block to receive input information with the help of substitution variables. Substitution variables cannot be used to output values, because no memory is allocated for them. SQL*Plus substitutes a variable before the PL/SQL block is sent to the database. Substitution variables usually are prefixed by the ampersand (&) or double ampersand (&&) characters.
Example:-
DECLARE
v_num number:=#
v_result number;
BEGIN
v_result := POWER(v_num, 2);
DBMS_OUTPUT.PUT_LINE ('The value of v_result is: '||v_result);
END;
/
Note:- Here "num" is the substitution variable.
Reserved Words:- These are the words that can not be used as a variable or literals.
Example:-
BEGIN,DECLARE,END,LOOP,CASE,SELECT,INTO,FROM
Example:- Smallest program in PLSQL
begin
null;
end;
/
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