plsql学习:cursor游标使用例子(1)

--PL/SQL supports three kinds of records: table-based, cursor-based,and programmer-defined.

/**

A table-based record is one whose structure is drawn from the list of columns in the table.

A cursor-based record is one whose structure matches the elements of a predefined cursor.

To create a table-based or cursor-based record, use the %ROWTYPE attribute:

record_name table_name or cursor_name%ROWTYPE

*/

-----------example A:--------

set serveroutput on

declare

vr_student student%rowtype

begin

select *

into vr_student

from student

where student_id = 156;

dbms_output.put_line(vr_student.first_name||' '||

vr_student.lase_name||' has an ID of 156');

exception

when no_data_found

then

reise_application_error(-2001,'the student '||

'is not in the database');

end;

----------example B:----------

set serveroutput on

declare

cursor c_zip is

select * from zipcode;

vr_zip c_zip%rowtype;

begin

open c_zip;

loop

fetch c_zip into vr_zip;

exit when c_zip%notfound;

dbms_output.put_line(vr_zip.zip||' '||vr_zip.city||' '||vr_zip.state);

end loop;

end;

----------example C:---------

set serveroutput on;

declare

type instructor_info is record

(first_name instructor.first_name%type,

last_name instructor.last_name%type,

sections number);

rv_instructor instructor_info;

begin

select rtrim(i.first_name),rtrim(i.last_name),count(*)

into rv_instructor

from instructor i,section s

where i.instructor_id = s.instructor_id

and i.instructor_id = 102

group by i.first_name,i.last_name;

dbms_output.put_line('instructor, '||rv_instructor.first_name||

' '||rv_instructor.last_name||

',teaches '||rv_instructor.sections||

'sections(s)');

exception

when no_data_found then

dbms_output.put_line('there is no such instructor');

end;

#######################################################################################

#

# Explicit Cursor Attributes

#----------------------------------------------------------------------------------

# CURSOR ATTRIBUTE SYNTAX DESCRIPTION

#----------------------------------------------------------------------------------

# A: %NOTFOUND cursor_name%NOTFOUND A Boolean attribute that returns TRUE if

# the previous FETCH did not return a row

# and FALSE if it did.

#----------------------------------------------------------------------------------

# B: %FOUND cursor_name%FOUND A Boolean attribute that returns TRUE if

# the previous FETCH returned a row and

# FALSE if it did not.

#----------------------------------------------------------------------------------

# C:%ROWCOUNT cursor_name%ROWCOUNT The number of records fetched from a

# cursor at that point in time.

#----------------------------------------------------------------------------------

# D:%ISOPEN cursor_name%ISOPEN A Boolean attribute that returns TRUE if

# the cursor is open and FALSE if it is not.

#----------------------------------------------------------------------------------

#######################################################################################

--example D:-----------

# Cursor attributes can be used with implicit cursors by using the prefix SQL, such as

# SQL%ROWCOUNT.

# If you use SELECT INTO syntax in your PL/SQL block, you will create an implicit cursor.You can

# then use these attributes on the implicit cursor.

set serveroutput on

declare

v_city zipcode.city%type;

begin

select city

into v_city

from zipcode

where zip = 07002;

if SQL%rowcount = 0;

then

dbms_output.put_line('******');

else if sql%rowcount = 0

then

dbms_output.put_line('******');

else

dbms_output.put_line('*******');

end if;

end;

--------example E:-------

declare

v_sid student.student_id%type;

cousor c_student is

select student_id

from student

where student_id < 110;

begin

open c_student;

loop

fetch c_student into v_sid;

exit when c_student%notfound;

dbms_output.put_line('student ID:'||v_sid);

end loop;

close c_student;

exception

when others

then

if c_student%isopen

then

close c_student;

end if;

end;

--------------example F:(Nest cusors)-------

set serveroutput on

declare

v_zip zipcode.zip%Type;

v_student_flag Char;

cursor c_zip is

select zip, city, state

from zipcode

where state = 'CT';

cursor c_student is

select first_name ,last_name

from student

where zip = v_zip;

bebin

for r_zip in c_zip

loop

v_student_flag := 'N';

v_zip := r_zip.zip;

dbms_output.put_line(chr(10));

dbms_output.put_line('students living in'||r_zip.city);

for r_student in c_student

loop

dbms_output.put_line(r_student.first_name||

' '||r_student.last_name);

v_student_flag := 'Y';

end loop;

if v_student_flag = 'N'

then

dbms_output.put_line('no student for this zipcode');

end if

end loop;

end ;

---------example G: using Current Of statement--------

declare

cursor c_stud_zip is

select s.student_id ,z.city

from student s, zipcode z

where z.city = 'Brookyn'

and s.zip = z.zip

for update of phone;

begin

for c_stud_zip in c_stud_zip

loop

dbms_output.put_line(r_stud_zip.student_id);

update student

set phone = '718'||Substr(phone,4)

where current of c_stud_zip;

end loop;

end;