PL/SQL is Oracle's procedural language used for triggers, stored procedures, and other database operations. It uses a basic structure of declare, begin, exception, and end sections. Within PL/SQL, you can declare variables and cursors, use conditional and loop logic, and handle exceptions. For example, one can declare a cursor to iterate through rows from a table, check conditions, and update other tables as needed.

1. SQL
1
Fall 2001 Database Systems 1
PL/SQL
• Oracle’s procedural language. Used for triggers, stored
procedures, etc.
• Overview
declare
<declarations section>
begin
<executable commands>
exception
<exception handling>
end;
Fall 2001 Database Systems 2
PL/SQL Example
declare
cursor item_cursor is select * from ITEMS ;
item_val item_cursor%ROWTYPE ;
cnt INTEGER(5) := 0 ;
begin
open item_cursor ;
loop
fetch item_cursor into item_val ;
exit when item_cursor%NOTFOUND ;
cnt := cnt + 1 ;
end loop ;
close item_cursor ;
if (cnt > 0)
then insert into item_count values(cnt) ;
end if ;
end ;
/

2. SQL
2
Fall 2001 Database Systems 3
PL/SQL
• Cursor properties
– %FOUND, %NOTFOUND : a record can/cannot be fetched from the
cursor
– %ISOPEN : the cursor has been opened
– %ROWCOUNT : the number of rows fetched from the cursor so far
– %TYPE : the data type of a column:
Iname item_cursor.name%TYPE
• Conditional logic
if <some condition>
then <some command>
elsif <some condition>
then <some command>
else <some command>
end if ;
Fall 2001 Database Systems 4
PL/SQL – Loops
• For loop:
for item_val in item_cursor
loop
end loop ;
//note no need for open/fetch/close
cursor commands in this case.
• While loop:
while cnt < 5
loop
end loop ;

3. SQL
3
Fall 2001 Database Systems 5
PL/SQL – exceptions
• Exceptions arise when a statement causes an error.
• Examples:
ACCESS_INTO_NULL
CURSOR_ALREADY_OPEN
DUP_VAL_ON_INDEX
INVALID_CURSOR
LOGIN_DENIED
NO_DATA_FOUND
NOT_LOGGED_ON
TOO_MANY_ROWS – select into stmt returns more
than one row
VALUE_ERROR
ZERO_DIVIDE
Fall 2001 Database Systems 6
PL/SQL
declare
cursor item_cursor is select I.iid, I.oid, count(B.bid) bidcnt
from items I, bids B where I.iid = B.iid
group by I.iid, I.oid ;
item_val item_cursor%ROWTYPE ;
begin
update owners set status = ‘B’ ;
for item_val in item_cursor
loop
if (item_val.bidcnt > 2)
then update owners set status = ‘G’
where oid = item_val.oid;
end if;
end loop ;
end ;
/