Oracle PL/SQL Tutorial/Cursor/ref cursor
Содержание
Create and use reference cursor
SQL>
SQL> create table big_table as select * from all_objects;
Table created.
SQL>
SQL> declare
2 c sys_refcursor;
3 type array is table of big_table%rowtype index by binary_integer;
4 l_rec array;
5 begin
6 for i in 1 .. 5
7 loop
8 open c for select * from big_table ORDER BY OWNER;
9 fetch c bulk collect into l_rec limit i*1000;
10 close c;
11 end loop;
12 end;
13 /
PL/SQL procedure successfully completed.
SQL>
SQL> drop table big_table;
Table dropped.
SQL>
Creating a REF CURSOR datatype
The REF CURSOR datatype cannot be used outside a PL/SQL environment.
There are two kinds of REF CURSOR types: weak and strong.
A weak REF CURSOR can point to any data set, as shown here:
declare
type weak_rcty is ref cursor;
c_weak rcty weak_rcty;
REF CURSOR custom type
SQL> CREATE TABLE book (
2 isbn CHAR(10) PRIMARY KEY,
3 category VARCHAR2(20),
4 title VARCHAR2(100),
5 num_pages NUMBER,
6 price NUMBER,
7 copyright NUMBER(4),
8 emp1 NUMBER,
9 emp2 NUMBER,
10 emp3 NUMBER
11 );
Table created.
SQL>
SQL> INSERT INTO book (isbn, category, title, num_pages, price, copyright, emp1, emp2, emp3)
2 VALUES ("1", "Database", "Oracle", 563, 39.99, 2009, 1, 2, 3);
1 row created.
SQL> INSERT INTO book (isbn, category, title, num_pages, price, copyright, emp1, emp2)
2 VALUES ("2", "Database", "MySQL", 765, 44.99, 2009, 4, 5);
1 row created.
SQL> INSERT INTO book (isbn, category, title, num_pages, price, copyright, emp1, emp2, emp3)
2 VALUES ("3", "Database", "SQL Server", 404, 39.99, 2001, 6, 7, 8);
1 row created.
SQL>
SQL>
SQL> SET SERVEROUTPUT ON ESCAPE OFF
SQL>
SQL> DECLARE
2
3 TYPE book_typ IS REF CURSOR RETURN book%ROWTYPE;
4 cv_book book_typ;
5 v_book book%ROWTYPE;
6
7 BEGIN
8
9 DBMS_OUTPUT.ENABLE(1000000);
10
11 OPEN cv_book FOR SELECT * FROM book WHERE isbn = "1";
12
13 FETCH cv_book INTO v_book;
14
15 DBMS_OUTPUT.PUT_LINE(v_book.title||" is "||v_book.price);
16
17 CLOSE cv_book;
18 END;
19 /
Oracle is 39.99
PL/SQL procedure successfully completed.
SQL>
SQL> drop table book;
Table dropped.
Reference cursor
SQL>
SQL> CREATE TABLE emp (
2 id NUMBER PRIMARY KEY,
3 fname VARCHAR2(50),
4 lname VARCHAR2(50)
5 );
Table created.
SQL>
SQL> INSERT INTO emp (id, fname, lname)VALUES (1, "A", "B");
1 row created.
SQL> INSERT INTO emp (id, fname, lname)VALUES (2, "C", "D");
1 row created.
SQL> INSERT INTO emp (id, fname, lname)VALUES (3, "Enn", "F");
1 row created.
SQL> INSERT INTO emp (id, fname, lname)VALUES (4, "G", "H");
1 row created.
SQL> INSERT INTO emp (id, fname, lname)VALUES (5, "G", "Z");
1 row created.
SQL>
SQL>
SQL> SET SERVEROUTPUT ON ESCAPE OFF
SQL>
SQL> CREATE OR REPLACE PROCEDURE emp_sel (cv_results IN OUT SYS_REFCURSOR)
2 IS
3 BEGIN
4 OPEN cv_results FOR SELECT id, fname, lname FROM emp;
5 END;
6 /
Procedure created.
SQL>
SQL> VARIABLE x REFCURSOR
SQL>
SQL> EXEC emp_sel(:x)
PL/SQL procedure successfully completed.
SQL>
SQL> print x
ID FNAME
---------- --------------------------------------------------
LNAME
--------------------------------------------------
1 A
B
2 C
D
3 Enn
F
4 G
H
5 G
Z
5 rows selected.
SQL>
SQL> drop table emp;
Table dropped.
SQL>
Reference value in a cursor by cursor variable
SQL>
SQL> -- create demo table
SQL> create table emp(
2 ID VARCHAR2(4 BYTE) NOT NULL,
3 fname VARCHAR2(10 BYTE),
4 lname VARCHAR2(10 BYTE),
5 Start_Date DATE,
6 End_Date DATE,
7 Salary Number(8,2),
8 City VARCHAR2(10 BYTE),
9 Description VARCHAR2(15 BYTE)
10 )
11 /
Table created.
SQL>
SQL> -- prepare data
SQL> insert into emp(ID, fname, lname, Start_Date, End_Date, Salary, City, Description)
2 values ("01","Jason", "Martin", to_date("19960725","YYYYMMDD"), to_date("20060725","YYYYMMDD"), 1234.56, "Toronto", "Programmer")
3 /
1 row created.
SQL> insert into emp(ID, fname, lname, Start_Date, End_Date, Salary, City, Description)
2 values("02","Alison", "Mathews", to_date("19760321","YYYYMMDD"), to_date("19860221","YYYYMMDD"), 6661.78, "Vancouver","Tester")
3 /
1 row created.
SQL> insert into emp(ID, fname, lname, Start_Date, End_Date, Salary, City, Description)
2 values("03","James", "Smith", to_date("19781212","YYYYMMDD"), to_date("19900315","YYYYMMDD"), 6544.78, "Vancouver","Tester")
3 /
1 row created.
SQL> insert into emp(ID, fname, lname, Start_Date, End_Date, Salary, City, Description)
2 values("04","Celia", "Rice", to_date("19821024","YYYYMMDD"), to_date("19990421","YYYYMMDD"), 2344.78, "Vancouver","Manager")
3 /
1 row created.
SQL> insert into emp(ID, fname, lname, Start_Date, End_Date, Salary, City, Description)
2 values("05","Robert", "Black", to_date("19840115","YYYYMMDD"), to_date("19980808","YYYYMMDD"), 2334.78, "Vancouver","Tester")
3 /
1 row created.
SQL> insert into emp(ID, fname, lname, Start_Date, End_Date, Salary, City, Description)
2 values("06","Linda", "Green", to_date("19870730","YYYYMMDD"), to_date("19960104","YYYYMMDD"), 4322.78,"New York", "Tester")
3 /
1 row created.
SQL> insert into emp(ID, fname, lname, Start_Date, End_Date, Salary, City, Description)
2 values("07","David", "Larry", to_date("19901231","YYYYMMDD"), to_date("19980212","YYYYMMDD"), 7897.78,"New York", "Manager")
3 /
1 row created.
SQL> insert into emp(ID, fname, lname, Start_Date, End_Date, Salary, City, Description)
2 values("08","James", "Cat", to_date("19960917","YYYYMMDD"), to_date("20020415","YYYYMMDD"), 1232.78,"Vancouver", "Tester")
3 /
1 row created.
SQL>
SQL>
SQL>
SQL> -- display data in the table
SQL> select * from emp
2 /
ID FNAME LNAME START_DAT END_DATE SALARY CITY
---- ---------- ---------- --------- --------- ---------- ----------
DESCRIPTION
---------------
01 Jason Martin 25-JUL-96 25-JUL-06 1234.56 Toronto
Programmer
02 Alison Mathews 21-MAR-76 21-FEB-86 6661.78 Vancouver
Tester
03 James Smith 12-DEC-78 15-MAR-90 6544.78 Vancouver
Tester
ID FNAME LNAME START_DAT END_DATE SALARY CITY
---- ---------- ---------- --------- --------- ---------- ----------
DESCRIPTION
---------------
04 Celia Rice 24-OCT-82 21-APR-99 2344.78 Vancouver
Manager
05 Robert Black 15-JAN-84 08-AUG-98 2334.78 Vancouver
Tester
06 Linda Green 30-JUL-87 04-JAN-96 4322.78 New York
Tester
ID FNAME LNAME START_DAT END_DATE SALARY CITY
---- ---------- ---------- --------- --------- ---------- ----------
DESCRIPTION
---------------
07 David Larry 31-DEC-90 12-FEB-98 7897.78 New York
Manager
08 James Cat 17-SEP-96 15-APR-02 1232.78 Vancouver
Tester
8 rows selected.
SQL> CREATE OR REPLACE PROCEDURE myProcedure
2 AS
3 CURSOR myCursor IS SELECT id, fname FROM emp;
4 TYPE firstNameType IS TABLE OF emp.fname%type INDEX BY emp.id%type;
5 ch firstNameType;
6 i integer := 0;
7 imax integer;
8 BEGIN
9 FOR j IN myCursor LOOP
10 i := i + 1;
11 ch(i) := j.fname;
12 END LOOP;
13 dbms_output.put_line(ch("James"));
14 END myProcedure;
15 /
Procedure created.
SQL>
SQL> exec myProcedure;
SQL>
SQL>
SQL>
SQL> -- clean the table
SQL> drop table emp
2 /
Table dropped.
SQL>
SQL>
SQL>
Timing a ref cursor
SQL>
SQL> declare
2 type rc is ref cursor;
3 l_rc rc;
4 l_dummy all_objects.object_name%type;
5 l_start number default dbms_utility.get_time;
6 begin
7 for i in 1 .. 1000
8 loop
9 open l_rc for
10 "select object_name
11 from all_objects
12 where object_id = :x"
13 using i;
14 fetch l_rc into l_dummy;
15 close l_rc;
16 end loop;
17 dbms_output.put_line
18 ( round( (dbms_utility.get_time-l_start)/100, 2 ) ||
19 " seconds..." );
20 end;
21 /
.63 seconds...
PL/SQL procedure successfully completed.
Elapsed: 00:00:00.70
SQL>
SQL> set timing off