Oracle PL/SQL Tutorial/Cursor/ref cursor

Материал из SQL эксперт
Перейти к: навигация, поиск

Create and use reference cursor

   <source lang="sql">

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></source>


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:



   <source lang="sql">

declare

 type weak_rcty is ref cursor;
 c_weak rcty weak_rcty;</source>
   
  

REF CURSOR custom type

   <source lang="sql">

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.</source>


Reference cursor

   <source lang="sql">

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></source>


Reference value in a cursor by cursor variable

   <source lang="sql">

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></source>


Timing a ref cursor

   <source lang="sql">

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</source>