1. 1
Agenda
Summary of last class
Loops
Simple Loops
WHILE Loops
FOR Loops
Records
Cursors
2. 2
Records
User-defined composite types
Provides a way to treat separate but logically related
variables as a unit
Similar to “structures” in C
Use the dot notation to refer to fields within a record
v_StudentInfo.FirstName := ‘John’;
In order to copy one record to another record, both records must
be of the same record type
3. 3
Records
Syntax:
DECLARE
TYPE t_StudentRecord IS RECORD(
Student_ID NUMBER(5),
FirstName VARCHAR2(20),
LastName VARCHAR2(20) );
v_StudentInfo t_StudentRecord;
BEGIN
-- Process data here
EXCEPTION
-- Error handling would go here
END;
/
Use the dot notation to refer
to fields within a record.
Example:
v_StudentInfo.FirstName := ‘John’;
4. 4
Records
To declare a record with the same
structure (i.e. fields & field types) as a
database row, use %ROWTYPE
Syntax:
DECLARE
v_StudentInfo student%ROWTYPE;
BEGIN
-- Process data here
EXCEPTION
-- Error handling would go here
END;
/
NOTE:
Any NOT NULL constraints
that are defined for a column
within the table will not be
applicable to the declared
record when %ROWTYPE is
used.
5. 5
Cursors
A pointer to the context area
Context area contains:
Number of rows processed by the statement
A pointer to the parsed representation of the statement
In the case of a query, the set of rows returned by the
query (i.e. the active set, active recordset)
Follows standard declaration and scoping
Naming Convention: c_CursorName
Cursor Types:
Explicit: user-defined
Implicit: system-defined
6. 6
Explicit Cursors
To use explicit cursors…
Declare the cursor
Open the cursor
Fetch the results into PL/SQL variables
Close the cursor
7. 7
Declaring Cursors
DECLARE
v_StudentID students.id%TYPE;
v_FirstName students.first_name%TYPE;
v_LastName students.last_name%TYPE;
CURSOR c_HistoryStudents IS
SELECT id, first_name, last_name
FROM students
WHERE major = ‘History’;
BEGIN
-- open cursor, fetch records & then close cursor here
END;
/
8. 8
OPEN Cursor
DECLARE
v_StudentID students.id%TYPE;
v_FirstName students.first_name%TYPE;
v_LastName students.last_name%TYPE;
CURSOR c_HistoryStudents IS
SELECT id, first_name, last_name
FROM students
WHERE major = ‘History’;
BEGIN
OPEN c_HistoryStudents;
-- fetch records & then close cursor here
END;
/
9. 9
FETCH Records
DECLARE
v_StudentID students.id%TYPE;
v_FirstName students.first_name%TYPE;
v_LastName students.last_name%TYPE;
CURSOR c_HistoryStudents IS
SELECT id, first_name, last_name
FROM students
WHERE major = ‘History’;
BEGIN
OPEN c_HistoryStudents;
LOOP
FETCH c_HistoryStudents INTO v_StudentID, v_FirstName, v_LastName;
EXIT WHEN c_HistoryStudents%NOTFOUND;
-- do something with the values that are now in the variables
END LOOP
-- close cursor here
END;/
10. 10
Close Cursor
DECLARE
v_StudentID students.id%TYPE;
v_FirstName students.first_name%TYPE;
v_LastName students.last_name%TYPE;
CURSOR c_HistoryStudents IS
SELECT id, first_name, last_name
FROM students
WHERE major = ‘History’;
BEGIN
OPEN c_HistoryStudents;
LOOP
FETCH c_HistoryStudents INTO v_StudentID, v_FirstName, v_LastName;
DBMS_OUTPUT.PUT_LINE(v_StudentID, v_FirstName, v_LastName);
EXIT WHEN c_HistoryStudents%NOTFOUND;
-- do something with the values that are now stored in the variables
END LOOP
CLOSE c_HistoryStudents;
END; /
11. 11
Cursor Attributes
Cursors have four attributes…
%FOUND
TRUE if the previous FETCH returned a row
Otherwise, FALSE
%NOTFOUND
TRUE if the previous FETCH did NOT return a row
Otherwise, FALSE
%ISOPEN
TRUE if the cursor is open,
Otherwise, FALSE
%ROWCOUNT
Returns the # of rows that have been fetched by the cursor
so far
12. 12
Cursor Fetch Loop: WHILE Loop
DECLARE
CURSOR c_HistoryStudents IS
SELECT id, first_name, last_name
FROM students
WHERE major = 'History';
v_StudentData c_HistoryStudents%ROWTYPE;
BEGIN
OPEN c_HistoryStudents;
FETCH c_HistoryStudents INTO v_StudentData;
WHILE c_HistoryStudents%FOUND LOOP
INSERT INTO registered_students (student_id, department, course)
VALUES (v_StudentData.ID, 'HIS', 301);
INSERT INTO temp_table (num_col, char_col)
VALUES (v_StudentData.ID, v_StudentData.first_name || ' ' ||
v_StudentData.last_name);
FETCH c_HistoryStudents INTO v_StudentData;
END LOOP;
CLOSE c_HistoryStudents;
END;/
13. 13
Take Home Exercise #1
Write an anonymous PL/SQL block that…
Defines a cursor that points to a record set that contains
the sailors’ names, reservation date and boat id where
the boat color is red
Opens the cursor
Uses a simple loop to fetch each record in the active set
Displays each last name, reservation date and boat id for
each record to the output screen
Schema
Sailor (sid, sname, rating, age)
Boat (bid, bname, color)
Reservation(sid, bid, day)
14. 14
Cursor with Bind Variable(s)
DECLARE
v_StudentID students.id%TYPE;
v_FirstName students.first_name%TYPE;
v_LastName students.last_name%TYPE;
v_Major students.major%TYPE;
CURSOR c_HistoryStudents IS
SELECT id, first_name, last_name
FROM students
WHERE major = v_Major;
BEGIN
v_Major := ‘History’;
OPEN c_HistoryStudents;
LOOP
FETCH c_HistoryStudents INTO v_StudentID, v_FirstName, v_LastName;
EXIT WHEN c_HistoryStudents%NOTFOUND;
-- do something with the values that are now stored in the variables
END LOOP
CLOSE c_HistoryStudents;
END; /
15. 15
Bind Variables
What are bind variables?
Variables that are referenced in the cursor
declaration
They must be declared BEFORE the cursor is
declared
i.e. variable must be declared before it can be used
The values of bind variables are examined ONLY
when the cursor is opened (at run time)
16. 16
Explicit Cursors with Bind
Variables
To use explicit cursors with bind variables…
Declare bind variables
Then declare the cursor
Assign values to bind variables
Open the cursor
Fetch the results into PL/SQL variables
Close the cursor
17. 17
Take Home Exercise #2
Modify your answer for Class Exercise #1
such that…
It uses bind variables for color of boat instead
of hard-coding the values in the WHERE clause
The FETCH is done inside of a WHILE loop
instead of inside of a simple loop.
18. 18
Implicit Cursors
Used for INSERT, UPDATE, DELETE and SELECT…
INTO queries
In SQL%NOTFOUND, SQL is called the implicit cursor
PL/SQL opens & closes implicit cursors, which is also
called SQL cursor
You don’t declare the implicit cursor
If the WHERE clause fails…
For SELECT…INTO statement, then NO_DATA_FOUND error
is raised instead of SQL%NOTFOUND
For UPDATEs and DELETEs, SQL%NOTFOUND is set to
TRUE
19. 19
Example of Implicit Cursor
BEGIN
UPDATE rooms
SET number_seats = 100
WHERE room_id = 99980;
-- If the previous UPDATE statement didn't match any rows,
-- insert a new row into the rooms table.
IF SQL%NOTFOUND THEN
INSERT INTO rooms (room_id, number_seats)
VALUES (99980, 100);
END IF;
END;
/
20. 20
Example of Implicit Cursor
BEGIN
UPDATE rooms
SET number_seats = 100
WHERE room_id = 99980;
-- If the previous UPDATE statement didn't match any rows,
-- insert a new row into the rooms table.
IF SQL%ROWCOUNT = 0 THEN
INSERT INTO rooms (room_id, number_seats)
VALUES (99980, 100);
END IF;
END;
21. 21
-- Example of SELECT…INTO and NO_DATA_FOUND
set serveroutput on
DECLARE
-- Record to hold room information.
v_RoomData rooms%ROWTYPE;
BEGIN
-- Retrieve information about room ID -1.
SELECT *
INTO v_RoomData
FROM rooms
WHERE room_id = -1;
-- The following statement will never be executed, since
-- control passes immediately to the exception handler.
IF SQL%NOTFOUND THEN
DBMS_OUTPUT.PUT_LINE('SQL%NOTFOUND is true!');
END IF;
EXCEPTION
WHEN NO_DATA_FOUND THEN
DBMS_OUTPUT.PUT_LINE('NO_DATA_FOUND raised!');
END;
/
23. 23
Summary of last class
Cursors
A pointer to the context area (active set)
Name begins with c_
Defined within the DECLARE section
Types: Explicit vs. Implicit
Explicit: (1) Declare, (2) Open, (3) Fetch & (4) Close
Bind variables
Variables that are referenced in the cursor declaration
Must be defined BEFORE the cursor
Values examined ONLY at run time
CURSOR c_HistoryStudents IS
SELECT id, first_name, last_name
FROM students
WHERE major = ‘History’;
24. 24
Take Home Exercise #1
DECLARE
CURSOR c_Reservations IS
SELECT s.sname, r.day, r.bid
FROM Sailor S, Reserve R, Boat B
WHERE R.sid = s.sid
AND R.bid = b.bid
AND B.color = ‘red’;
v_Reservation c_Reservations%ROWTYPE;
BEGIN
OPEN c_Reservations;
LOOP
FETCH c_Reservations INTO v_Reservation;
EXIT WHEN c_Reservations%NOTFOUND;
DBMS_OUTPUT.PUT_LINE(v_Reservation.sname||’ ‘||v_Reservation.day||’
v_Reservation.bid);
END LOOP;
CLOSE c_Reservations;
END;/
Reserve
sid bid day
22 101 10/10/98
22 102 10/10/98
22 103 10/8/98
22 104 10/7/98
31 102 11/10/98
31 103 11/6/98
31 104 11/12/98
64 101 9/5/98
64 102 9/8/98
74 103 9/8/98
Boat
bid bname color
101 Interlake blue
102 Interlake red
103 Clipper green
104 Marine red
Sailor
sid sname rating age
22 Dustin 7 45.0
29 Brutus 1 33.0
31 Lubber 8 55.5
32 Andy 8 25.5
58 Rusty 10 35.0
64 Horatio 7 35.0
71 Zorba 10 16.0
74 Horatio 9 35.0
85 Art 3 25.5
95 Bob 3 63.5
25. 25
Cursor Attributes
Cursors have four attributes…
%FOUND
TRUE if the previous FETCH returned a row
Otherwise, FALSE
%NOTFOUND
TRUE if the previous FETCH did NOT return a row
Otherwise, FALSE
%ISOPEN
TRUE if the cursor is open,
Otherwise, FALSE
%ROWCOUNT
Returns the # of rows that have been fetched by the cursor
so far
26. 26
Implicit Cursors
Used for INSERT, UPDATE, DELETE and SELECT…
INTO queries
In SQL%NOTFOUND, SQL is called the implicit cursor
PL/SQL opens & closes implicit cursors, which is also
called SQL cursor
You don’t declare the implicit cursor
If the WHERE clause fails…
For SELECT…INTO statement, then NO_DATA_FOUND error
is raised instead of SQL%NOTFOUND
For UPDATEs and DELETEs, SQL%NOTFOUND is set to
TRUE
27. 27
Exceptions & Exception Handling
What are exceptions & exception handlers?
The method by which the program reacts & deals
with runtime errors
How do they work?
When a runtime error occurs, an exception is
raised
Then control is passed to the exception handler
(i.e. the EXCEPTION section)
Once control is passed to the exception handler,
there is no way to return to the executable section
28. 28
Declaring (Explicit) Exceptions
How are explicit exceptions declared?
Defined within the DECLARE section
Defined using the keyword data type EXCEPTION
Name starts with e_
Example:
DECLARE
e_TooManyStudents EXCEPTION;
v_CurrentStudents NUMBER(3);
v_MaxStudentsNUMBER(3);
BEGIN
-- process data here
EXCEPTION
-- handle exceptions here
END;/
29. 29
Raising Exceptions
How are exceptions used?
Within the executable section
Test a condition
If the condition evaluates to true, then use the
keyword RAISE to raise an exception
Can use the RAISE keyword with either predefined
exceptions or user-defined exceptions
30. 30
Raising Exceptions
DECLARE
e_TooManyStudents EXCEPTION;
v_CurrentStudents NUMBER(3);
v_MaxStudents NUMBER(3);
BEGIN
SELECT current_students, max_students
INTO v_CurrentStudents, v_MaxStudents
FROM classes
WHERE department = 'HIS' AND course = 101;
IF v_CurrentStudents > v_MaxStudents THEN
RAISE e_TooManyStudents;
END IF;
EXCEPTION
-- handle exceptions here
END;/
31. 31
Handling Exceptions
Syntax
DECLARE
e_TooManyStudents EXCEPTION;
BEGIN
-- process data here
EXCEPTION
WHEN exception_Name1 THEN
statements;
WHEN exception_Name2 THEN
statements;
WHEN OTHERS THEN
statements;
END;/
An exception can be handled by at most one
handler!
32. 32
Handling Exceptions
DECLARE
e_TooManyStudents EXCEPTION;
v_CurrentStudents NUMBER(3);
v_MaxStudents NUMBER(3);
BEGIN
SELECT current_students, max_students
INTO v_CurrentStudents, v_MaxStudents
FROM classes
WHERE department = 'HIS' AND course = 101;
IF v_CurrentStudents > v_MaxStudents THEN
RAISE e_TooManyStudents;
END IF;
EXCEPTION
WHEN e_TooManyStudents THEN
INSERT INTO log_table (info)
VALUES ('History 101 has ' || v_CurrentStudents ||
'students: max allowed is ' || v_MaxStudents);
WHEN OTHERS THEN
INSERT INTO log_table (info) VALUES ('Another error occurred');
END;/
33. 33
Handling Exceptions
Built-in Functions
SQLCODE
Returns the error code associated with the error
Returns a value of 1 for user-defined exception
Returns a value of 0 if no error with the last executed
statement
SQLERRM
Returns the text of the error message
Maximum length of an Oracle message is 512 characters
Returns “User-defined Exception” for user-defined exception
RAISE_APPLICATION_ERROR
RAISE_APPLICATION_ERROR(error#, error_message);
Valid error #s: -20,000 and –20,999
Error_Message MUST be less than 512 characters
35. 35
Key Concepts: PL/SQL Block
Basic building block/unit of PL/SQL programs
Three possible sections of a block
Declarative section (optional)
Executable section (required)
Delimiters : BEGIN, END
Exception handling (optional)
A block performs a logical unit of work in the
program
Blocks can be nested
36. 36
Key Concepts: IF-THEN-ELSE &
CASE
IF boolean_expression1 THEN
sequence_of_statements;
[ELSIF boolean_expression2
THEN
sequence_of_statements]
[ELSE
sequence_of_statements]
END IF;
Either specify test case after CASE
keyword & OR specify test after
WHEN keyword
CASE
WHEN boolean_expression1 THEN
sequence_of_statements;
WHEN boolean_expression2 THEN
sequence_of_statements;
ELSE
sequence_of_statements;
END CASE;
37. 37
Key Concepts: PL/SQL Loops
Used to execute a sequence of statements repeatedly
When the number of iterations is unknown
Simple loops: executes at least once
WHILE loops: executes while the condition is true
When the number of iterations is known in advance
Numeric FOR Loops: executes a specific number of times
SIMPLE LOOP
LOOP
sequence_of_statements;
EXIT WHEN condition;
END LOOP;
WHILE LOOP
WHILE condition LOOP
sequence_of_statements;
END LOOP;
FOR LOOP
FOR loop_Counter IN IN [REVERSE] low..high
LOOP sequence_of_statements;
END LOOP;
38. 38
Key Concepts: Records
Records
Explicit
Name begins with t_
Once declared, can be used to declare other variables
TYPE t_StudentRecord IS RECORD(
Student_ID NUMBER(5),
FirstName VARCHAR2(20),
LastName VARCHAR2(20));
v_StudentInfo t_StudentRecord;
Implicit
%ROWTYPE
Declares a record with the same structure as
v_StudentInfo student%ROWTYPE
Use dot notation to refer to fields within record
39. 39
Key Concepts: Cursors
Cursors
A pointer to the context area (active set)
Name begins with c_
Types: Explicit vs. Implicit
Explicit: (1) Declare, (2) Open, (3) Fetch & (4) Close
Bind variables
Variables that are referenced in the cursor declaration
Must be defined BEFORE the cursor
Values examined ONLY at run time
CURSOR c_HistoryStudents IS
SELECT id, first_name, last_name
FROM students
WHERE major = ‘History’;
40. 40
Key Concepts: Cursors
Explicit for SELECT statement
Implicit for all other DML statements
Used for INSERT, UPDATE, DELETE and SELECT…INTO queries
PL/SQL opens & closes implicit cursors, which is called SQL
cursor
If the WHERE clause fails…
For SELECT…INTO statement, then NO_DATA_FOUND error is
raised instead of SQL%NOTFOUND
For UPDATEs and DELETEs, SQL%NOTFOUND is set to TRUE
Four attributes: %FOUND, %NOTFOUND, %ISOPEN,
%ROWCOUNT
41. 41
Key Concepts: Exceptions &
Exception Handling
The method by which the program reacts & deals
with runtime errors
When a runtime error occurs, an exception is
raised & control passes to the EXCEPTION section
Once control is passed to the exception handler,
there is no way to return to the executable section
User-defined exceptions
Defined using the keyword data type EXCEPTION
Use the keyword RAISE to raise an exception
42. 42
Key Concepts: Exceptions &
Exception Handling
Pre-defined exceptions
NO_DATA_FOUND
no data found in SELECT…INTO
TOO_MANY_ROWS
SELECT…INTO produces more than one row
INVALID_CURSOR
Cursor already closed
CURSOR_ALREADY_OPEN
Cursor already open
ZERO_DIVIDE
Division by zero
INVALID_NUMBER
Data is not numeric
(see book for others)
43. 43
Key Concepts: Exceptions &
Exception Handling
Built-in Functions
SQLCODE
Returns the error code associated with the error
Returns a value of 1 for user-defined exception
Returns a value of 0 if no error with the last executed statement
SQLERRM
Returns the text of the error message
Maximum length of an Oracle message is 512 characters
Returns “User-defined Exception” for user-defined exception
RAISE_APPLICATION_ERROR
RAISE_APPLICATION_ERROR(error#, error_message);
Valid error #s: -20,000 and –20,999
Error_Message MUST be less than 512 characters
Used in procedures and functions
44. 44
Key Concepts: Exceptions &
Exception Handling
Syntax
DECLARE
e_TooManyStudents EXCEPTION;
BEGIN
-- process data here
EXCEPTION
WHEN exception_Name1 THEN
statements;
WHEN exception_Name2 THEN
statements;
WHEN OTHERS THEN
statements;
END;/
An exception can be handled by at most one handler!
45. 45
Key Concepts: Naming
Conventions
Item Naming Convention Note
primary keys *_pk * = tablename
*_fk1
*_fk2
*_fk#
*_u1 * = tablename
*_u2 * = tablename
*_u# # represents a sequential number
*_ck1 * = tablename
*_ck2 * = tablename
*_ck# # represents a sequential number
sequences *_sequence * = field name
script files *.sql * can be any name you choose
spooled files *.lst * can be any name you choose (e.g. TEST.LST)
cursors c_
exceptions e_
records t_ Explicit records
variables v_
foreign keys * = tablename; # = a sequential number
unique keys
checks
47. 47
DML in PL / SQL
Select
SELECT statement in PL/SQL retrieves
data from a database table into:
PL/SQL record
set of PL/SQL variables
Using SELECT in PL/SQL should only
return one row
When you need to retrieve more than
one row from a table use a cursor
48. 48
DML in PL / SQL
Select Syntax
SELECT { * | select_list_item }
INTO { PL/SQL_record | variables}
FROM table_reference
WHERE where_clause
each variable must be compatible with its
associated select list item
count of variables must be same as
number of items in list
record should contain fields that
correspond to the select list in type and
count
50. 50
DML in PL / SQL
Insert
The INSERT statement inserts data into a
database table
There are two variations of the INSERT
command
add one row to a table using the specified
VALUES list
add one or several rows when the insert
command uses a SELECT statement
51. 51
DML in PL / SQL
Insert Syntax
INSERT INTO table_reference
[(column_names)]
{VALUES (expression) | select_statement}
use column names when the values
are listed in a different order than as defined
during table creation
Only a portion of the columns of the table
are used during insert
table definition remains unchanged after
the new row is inserted
52. 52
DML in PL / SQL
Insert
The word VALUES must precede the
list of data to be inserted
Regarding the values in the list:
a character string must be in single
quotes
numbers can stand by themselves
dates must be in single quotes
In the default Oracle date format
Converted using TO_DATE function (this is
the suggested method)
53. 53
Insert
Using Built-in Functions
You can modify the contents of the values
before they are entered into a column of a
table
by a VALUES list
from a SELECT statement
Use any of the built-in functions supported
by PL/SQL
character
date functions
numeric
conversion
55. 55
DML in PL / SQL
Insert with Select
It is also possible to insert rows into a
table using the results of a SELECT
statement
The results of a SELECT statement
can return one or several rows based on
the WHERE clause
can be a mix of columns from one or
more tables
56. 56
DML in PL / SQL
Update
Requires setting specific values for
each column you wish to change
Specifying which row or rows to
modify using a WHERE clause
You can use built-in functions in
setting a value for the update
57. 57
Update in PL / SQL
Embedded SELECT
It is possible to set values in an
UPDATE by embedding a SELECT
statement right in the middle of it
SELECT has its own WHERE clause
UPDATE has its own WHERE clause to
affect the rows
You must be certain that the SELECT
will return no more than one row
58. 58
Embedded SELECT
BEGIN
UPDATE comfort set Midnight =
(SELECT temperature
FROM weather
WHERE city = ‘MANCHESTER’)
WHERE city = ‘WALPOLE’
AND SampleDate = TO_DATE (’22-DEC-1999’, ‘DD-MON-YYYY’);
END;
59. 59
DML in PL / SQL
Delete
Removing a row or rows from a table
WHERE clause is necessary to
removing only the rows you intend
DELETE without the where clause will
delete all of the rows of a table
61. 61
DML in PL / SQL
Truncate
Another command for deleting records
from a table is the TRUNCATE command
TRUNCATE TABLE students;
Does not operate the same as DELETE
deletes all rows from a table
cannot be rolled back
records are unrecoverable
does not run any DELETE triggers
does not record any information in a snapshot
log
62. 62
DML in PL / SQL
WHERE Clause
The SELECT, UPDATE, and DELETE
statements all include the WHERE clause
Defines the active set (set of rows):
returned by a SELECT query
Acted upon by an UPDATE or DELETE
Consists of conditions, joined together by
the boolean operators AND, OR, and NOT
Conditions usually take the form of
comparisons using the relational operators
(such as: =, <>, >, >=, <, <=)
63. 63
DML in PL / SQL
WHERE Clause with Cursor
The UPDATE, and DELETE statements
both include a WHERE clause with a
special syntax
the WHERE CURRENT OF is used with a
cursor definition
often processing done in a fetch loop
modifies the rows that have been
retrieved by a cursor
64. 64
DML in PL / SQL
WHERE Clause with Cursor
This method consists of two parts:
the FOR UPDATE clause in the cursor
declaration
the WHERE CURRENT OF clause in an
UPDATE or DELETE statement
66. 66
forupdat.sql (cont.)
BEGIN
FOR v_StudentInfo IN c_RegisteredStudents LOOP
SELECT num_credits
INTO v_NumCredits
FROM classes
WHERE department = 'HIS'
AND course = 101;
UPDATE students
SET current_credits = current_credits + v_NumCredits
WHERE CURRENT OF c_RegisteredStudents;
END LOOP;
COMMIT;
END;
67. 67
DML in PL / SQL
Synonyms
It is possible to create a synonym for
a:
table
view
sequence
stored
procedure
function
package
68. 68
DML in PL / SQL
Synonyms
The syntax for creating a synonym is:
CREATE SYNONYM synonym_name FOR
reference;
Where:
synonym_name – name of your synonym
reference – schema object being referenced
69. 69
Pseudocolums
Currval and Nextval
CURRVAL and NEXTVAL are used with
sequences
A sequence is an Oracle object used
to generate unique numbers
Once created, you can access it with
its name by:
sequence.CURRVAL
sequence.NEXTVAL
70. 70
Pseudocolums
Currval and Nextval
Sequence values can be used in:
SELECT list of a query
VALUES clause of an INSERT
SET clause of an UPDATE
Sequence values cannot be used in:
WHERE clause
PL/SQL statement
![36
Key Concepts: IF-THEN-ELSE &
CASE
IF boolean_expression1 THEN
sequence_of_statements;
[ELSIF boolean_expression2
THEN
sequence_of_statements]
[ELSE
sequence_of_statements]
END IF;
Either specify test case after CASE
keyword & OR specify test after
WHEN keyword
CASE
WHEN boolean_expression1 THEN
sequence_of_statements;
WHEN boolean_expression2 THEN
sequence_of_statements;
ELSE
sequence_of_statements;
END CASE;](https://image.slidesharecdn.com/plsql-sample-250410210435-9bc50723/85/PLplsql-study-aboutmsnsjskakajsjslajwvsbsns-36-320.jpg)
![37
Key Concepts: PL/SQL Loops
Used to execute a sequence of statements repeatedly
When the number of iterations is unknown
Simple loops: executes at least once
WHILE loops: executes while the condition is true
When the number of iterations is known in advance
Numeric FOR Loops: executes a specific number of times
SIMPLE LOOP
LOOP
sequence_of_statements;
EXIT WHEN condition;
END LOOP;
WHILE LOOP
WHILE condition LOOP
sequence_of_statements;
END LOOP;
FOR LOOP
FOR loop_Counter IN IN [REVERSE] low..high
LOOP sequence_of_statements;
END LOOP;](https://image.slidesharecdn.com/plsql-sample-250410210435-9bc50723/85/PLplsql-study-aboutmsnsjskakajsjslajwvsbsns-37-320.jpg)
![51
DML in PL / SQL
Insert Syntax
INSERT INTO table_reference
[(column_names)]
{VALUES (expression) | select_statement}
use column names when the values
are listed in a different order than as defined
during table creation
Only a portion of the columns of the table
are used during insert
table definition remains unchanged after
the new row is inserted](https://image.slidesharecdn.com/plsql-sample-250410210435-9bc50723/85/PLplsql-study-aboutmsnsjskakajsjslajwvsbsns-51-320.jpg)
