Blocks in PL/SQL

In PL/SQL, All statements are classified into units that is called Blocks. PL/SQL blocks can include variables, SQL statements, loops, constants, conditional statements and exception handling. Blocks can also build a function or a procedure or a package.

The Declaration section: Code block start with a declaration section, in which memory variables, constants, cursors and other oracle objects can be declared and if required initialized.

The Begin section: Consist of set of SQL and PL/SQL statements, which describe processes that have to be applied to table data. Actual data manipulation, retrieval, looping and branching constructs are specified in this section.

The Exception section: This section deals with handling errors that arise during execution data manipulation statements, which make up PL/SQL code block. Errors can arise due to syntax, logic and/or validation rule.

The End section: This marks the end of a PL/SQL block.

 Broadly, PL/SQL blocks are two types: Anonymous blocks and Named blocks are as follows:

1. Anonymous blocks: In PL/SQL, That’s blocks which is not have header are known as anonymous blocks. These blocks do not form the body of a function or triggers or procedure. Example: Here a code example of find greatest number with Anonymous blocks. 

SQL

DECLARE
    -- declare variable a, b and c
    -- and these three variables datatype are integer
   a number;
   b number;
   c number;
BEGIN
   a:= 10;
   b:= 100;
    --find largest number
    --take it in c variable
   IF a > b THEN
      c:= a;
   ELSE
      c:= b;
   END IF;
   dbms_output.put_line(' Maximum number in 10 and 100: ' || c);
END;
/
-- Program End

Output:

Maximum number in 10 and 100: 100

2. Named blocks: That’s PL/SQL blocks which having header or labels are known as Named blocks. These blocks can either be subprograms like functions, procedures, packages or Triggers. Example: Here a code example of find greatest number with Named blocks means using function. 

SQL

DECLARE

    -- declare variable a, b and c
    -- and these three variables datatype are integer
DECLARE
   a number;
   b number;
   c number;
   --Function return largest number of
   -- two given number
FUNCTION findMax(x IN number, y IN number)
RETURN number
IS
    z number;
BEGIN
   IF x > y THEN
      z:= x;
   ELSE
      Z:= y;
   END IF;
   RETURN z;
END;
BEGIN
   a:= 10;
   b:= 100;
   c := findMax(a, b);
   dbms_output.put_line(' Maximum number in 10 and 100 is: ' || c);
END;
/
-- Program End

Output:

Maximum number in 10 and 100: 100