1. PL/SQL Scripting in Oracle:
everything you wanted to know but were afraid to ask.
Haley Miller

2. Questions I will answer
What is PL/SQL?
What are its Advantages
What are its components?
What is the difference between procedures and functions?
How is SQL incorporated into PL/SQL
What does the code actually look like?
Where did you get all this information?

3. What is PL/SQL? Oracle-specific SQL-based language
conglomeration of SQL and a traditional programming languages
allows loops, declarations, branches to subroutines and assignments
procedural, transactional processing language that extends oracle and allows data manipulation not possible in SQL alone

4. Advantages (abridged)
Gives programmer control
can create constraints other than those allowed in SQL
Oracle allows SOME control relating to values entered into the tables, but some applications may require other constraints:
relate to another record
that apply only in a certain instance (if fieldA=x, then fieldB >90)
organizes repetitive tasks in to logical units

5. Programmer control: (continued)
extended error handling
more specific error messages
subroutines in case of error
on this error and if value>x then do SubroutineA
on this error and if value<=x then so SubroutineB
flow control
specify forms and events based on input or actions
triggers
subprograms that the database executes automatically in response to specified events.

6. Advantages [continued] (abridged)
Easy on the server
The PL/SQL engine can process an entire blocks of code at once; even one with multiple SQL statements in one call.
store compiled code directly in the database.
This enables any number of applications or users to share the same functions and procedures; once a given block of code is loaded into memory, any number of users can use the same copy of it simultaneously (although behavior is as though each user had her own copy)

7. Structure and Syntax Three sections: this example: Declarative
Executable
Exception-handling
this example:
a declarative section and an executable block consisting of 2 sub-blocks
Semi colons terminate lines
/* */ indicate comments

8. The DECLARE Section
define local variables, constants, types, exceptions, and nested subprograms. PL/SQL has a forward declaration, but you can use it only for subprograms. Therefore, you must define all variables, constants, and types before referencing them.
begins with the keyword DECLARE and ends when the keyword BEGIN signals the arrival of the EXECUTABLE section

9. The EXECUTABLE Section
actual code that the block executes. This is the only part of the block that must always be present.
SQL statements written here
Begins with the word Begin and ends with the word end
May have several begin/end statements with in sub blocks

10. The EXECUTABLE Section.
PL/SQL supports the following kinds of flow-control statements:
IF statements
Basic loops
FOR loops
WHILE loops
GOTO statements

11. SQL within PL/SQL Placed in the exectution section very few changes:
Insert, select, update, delete etc are all used here along with variables, conditions

12. The EXCEPTION Section
For handling runtime errors and warnings.

13. Procedures Vs. Functions
Two types of blocks:
function is used in an expression and returns a value to that expression
computes a value as part of the expression, contains a return value and MUST return a value
procedure is invoked as a standalone statement and passes values to the calling program only through parameters

15. Parameters: Used to pass to and from the calling environment
Three modes:
In - contains a value passed from the calling environment
Out - contains a value returned to the calling environment
In/Out - contains a value passed to and returned to the calling environment: often values is modified buy subprogram

17. Structure of Procedure and Functions
PROCEDURE procedure_name (param_name datatype, param_name datatype...) IS {local declarations} BEGIN {executable code} EXCEPTION END;
FUNCTION function_name (param_name, param_name datatype...) RETURN datatype IS {local declarations} BEGIN {executable code} EXCEPTION {local exception handlers} END;

18. A REALLY SIMPLE Example
A simple example
Commit;
this line of code commits the record in a given form to a table. It can be hooked to a button on the form and is called a trigger

19. Example: Insert
Values from the declare section (in brown) a inserted in to the table via the executable section

20. Example: Delete with constant
Close_stat is a constant specifed in the declare section and called in the Where clause of the Delete Statement

21. A word about limitations
PL/SQL elements must exist at run-time:
the is not a DDL (data definition language)
this example is not correct

22. References Overview of the Oracle7 Server, SQL, and PL/SQL
/ows-adoc/ap1serv.htm
The ORACLE PL/SQL CBT in Ileana’s office
installed in KitKat in Mc104
NetG’s PL/SQL CBT