Oracle管道函数(Pipelined Table Function)介绍

CREATE OR REPLACE PACKAGE pkg1 AS
    TYPE numset_t IS TABLE NUMBER;
    FUNCTION f1(x NUMBER) RETURN numset_t PIPELINED;
END pkg1;

CREATE OR REPLACE PACKAGE BODY pkg1 AS
    FUNCTION f1(x NUMBER) RETURN numset_t PIPELINED IS
        BEGIN
            FOR i IN 1..x LOOP
                PIPE ROW(i);
            END LOOP;
            RETURN;
        END;
END pkg1;

SELECT * FROM TABLE(pkg1.f1(5));

CREATE OR REPLACE PACKAGE refcur_pkg IS
  TYPE refcur_t IS REF CURSOR RETURN emp%ROWTYPE;
  TYPE outrec_typ IS RECORD ( 
    var_num    NUMBER(6),
    var_char1  VARCHAR2(30),
    var_char2  VARCHAR2(30));
  TYPE outrecset IS TABLE OF outrec_typ;
 FUNCTION f_trans(p refcur_t) 
      RETURN outrecset PIPELINED;
END refcur_pkg;

CREATE OR REPLACE PACKAGE BODY refcur_pkg IS
  FUNCTION f_trans(p refcur_t) 
   RETURN outrecset PIPELINED IS
    out_rec outrec_typ;
    in_rec  p%ROWTYPE;
  BEGIN
  LOOP
    FETCH p INTO in_rec;
    EXIT WHEN p%NOTFOUND;
    -- first row
    out_rec.var_num := in_rec.empno;
    out_rec.var_char1 := in_rec.ename;
    out_rec.var_char2 := in_rec.mgr;
    PIPE ROW(out_rec);
    -- second row
    out_rec.var_num := in_rec.deptno;
    out_rec.var_char1 := in_rec.deptno;
    out_rec.var_char2 := in_rec.job;
    PIPE ROW(out_rec);
  END LOOP;
  CLOSE p;
  RETURN;
  END;
END refcur_pkg;

SELECT * FROM TABLE(
   refcur_pkg.f_trans(CURSOR(SELECT * FROM emp WHERE empno=7782)));

-- Define the ref cursor types
CREATE PACKAGE refcur_pkg IS
  TYPE refcur_t1 IS REF CURSOR RETURN employees%ROWTYPE;
  TYPE refcur_t2 IS REF CURSOR RETURN departments%ROWTYPE;  
  TYPE outrec_typ IS RECORD ( 
    var_num    NUMBER(6),
    var_char1  VARCHAR2(30),
    var_char2  VARCHAR2(30));
  TYPE outrecset IS TABLE OF outrec_typ;
  FUNCTION g_trans(p1 refcur_t1, p2 refcur_t2) 
    RETURN outrecset PIPELINED;
END refcur_pkg;
/

CREATE PACKAGE BODY refcur_pkg IS
FUNCTION g_trans(p1 refcur_t1, p2 refcur_t2) 
    RETURN outrecset PIPELINED IS
    out_rec outrec_typ;
    in_rec1 p1%ROWTYPE;
    in_rec2 p2%ROWTYPE;
BEGIN
  LOOP
    FETCH p2 INTO in_rec2;
    EXIT WHEN p2%NOTFOUND;
  END LOOP;
  CLOSE p2;
  LOOP
    FETCH p1 INTO in_rec1;
    EXIT WHEN p1%NOTFOUND;
    -- first row
    out_rec.var_num := in_rec1.employee_id;
    out_rec.var_char1 := in_rec1.first_name;
    out_rec.var_char2 := in_rec1.last_name;
    PIPE ROW(out_rec);
    -- second row
    out_rec.var_num := in_rec2.department_id;
    out_rec.var_char1 := in_rec2.department_name;
    out_rec.var_char2 := TO_CHAR(in_rec2.location_id);
    PIPE ROW(out_rec);
  END LOOP;
  CLOSE p1;
  RETURN;
END;
END refcur_pkg;
/

-- SELECT query using the g_trans table function
SELECT * FROM TABLE(refcur_pkg.g_trans(
  CURSOR(SELECT * FROM employees WHERE department_id = 60),
  CURSOR(SELECT * FROM departments WHERE department_id = 60)));

CREATE TABLE gradereport (student VARCHAR2(30), subject VARCHAR2(30),
                          weight NUMBER, grade NUMBER);
INSERT INTO gradereport VALUES(‘Mark‘, ‘Physics‘, 4, 4);
INSERT INTO gradereport VALUES(‘Mark‘,‘Chemistry‘, 4, 3);
INSERT INTO gradereport VALUES(‘Mark‘,‘Maths‘, 3, 3);
INSERT INTO gradereport VALUES(‘Mark‘,‘Economics‘, 3, 4);

CREATE PACKAGE pkg_gpa IS
  TYPE gpa IS TABLE OF NUMBER;
  FUNCTION weighted_average(input_values SYS_REFCURSOR)
    RETURN gpa PIPELINED;
END pkg_gpa;
/
CREATE PACKAGE BODY pkg_gpa IS
FUNCTION weighted_average(input_values SYS_REFCURSOR)
  RETURN gpa PIPELINED IS
  grade NUMBER;
  total NUMBER := 0;
  total_weight NUMBER := 0;
  weight NUMBER := 0;
BEGIN
-- The function accepts a ref cursor and loops through all the input rows
  LOOP
     FETCH input_values INTO weight, grade;
     EXIT WHEN input_values%NOTFOUND;
-- Accumulate the weighted average
     total_weight := total_weight + weight;
     total := total + grade*weight;
  END LOOP;
  PIPE ROW (total / total_weight);
  RETURN; -- the function returns a single result
END;
END pkg_gpa;
/
-- the query result comes back as a nested table with a single row
-- COLUMN_VALUE is a keyword that returns the contents of a nested table
SELECT w.column_value "weighted result" FROM TABLE(
       pkg_gpa.weighted_average(CURSOR(SELECT weight, grade FROM gradereport))) w;