一 介绍
像游标cursor一样,游标变量ref cursor指向指定查询结果集当前行。游标变量显得更加灵活因为其声明并不绑定指定查询。
其主要运用于PLSQL函数或存储过程以及其他编程语言java等程序之间作为参数传递。
不像游标的一点,游标变量没有参数。
游标变量具有以下属性:
(%FOUND, %NOTFOUND, %ISOPEN, and %ROWCOUNT)
二 用法介绍:
1、声明格式:
DECLARE
TYPE DeptCurTyp IS REF CURSOR RETURN departments%ROWTYPE;
2、游标变量又分为强类型strong(with a return type)和弱类型(with no return type):
DECLARE
TYPE empcurtyp IS REF CURSOR RETURN employees%ROWTYPE; -- 强类型
TYPE genericcurtyp IS REF CURSOR; -- 弱类型
cursor1 empcurtyp;
cursor2 genericcurtyp;
my_cursor SYS_REFCURSOR; -- 使用预定义游标变量sys_refcursor
TYPE deptcurtyp IS REF CURSOR RETURN departments%ROWTYPE;
dept_cv deptcurtyp; -- 声明游标变量
或是返回record类型:
DECLARE
TYPE EmpRecTyp IS RECORD (
employee_id NUMBER,
last_name VARCHAR2(25),
salary NUMBER(8,2));
TYPE EmpCurTyp IS REF CURSOR RETURN EmpRecTyp;
emp_cv EmpCurTyp; -- declare cursor variable
3、使用游标变量作为参数传递:
DECLARE TYPE empcurtyp IS REF CURSOR RETURN employees%ROWTYPE; emp empcurtyp; -- after result set is built, process all the rows inside a single procedure -- rather than calling a procedure for each row PROCEDURE process_emp_cv (emp_cv IN empcurtyp) IS person employees%ROWTYPE; BEGIN DBMS_OUTPUT.PUT_LINE('-----'); DBMS_OUTPUT.PUT_LINE('Here are the names from the result set:'); LOOP FETCH emp_cv INTO person; EXIT WHEN emp_cv%NOTFOUND; DBMS_OUTPUT.PUT_LINE('Name = ' || person.first_name || ' ' || person.last_name); END LOOP; END; BEGIN -- First find 10 arbitrary employees. OPEN emp FOR SELECT * FROM employees WHERE ROWNUM < 11; process_emp_cv(emp); CLOSE emp; -- find employees matching a condition. OPEN emp FOR SELECT * FROM employees WHERE last_name LIKE 'R%'; process_emp_cv(emp); CLOSE emp; END; /
DECLARE TYPE empcurtyp IS REF CURSOR RETURN employees%ROWTYPE; emp_cv empcurtyp; BEGIN IF NOT emp_cv%ISOPEN THEN -- open cursor variable OPEN emp_cv FOR SELECT * FROM employees; END IF; CLOSE emp_cv; END; /
CREATE PACKAGE emp_data AS TYPE empcurtyp IS REF CURSOR RETURN employees%ROWTYPE; PROCEDURE open_emp_cv (emp_cv IN OUT empcurtyp); END emp_data; / CREATE PACKAGE BODY emp_data AS PROCEDURE open_emp_cv (emp_cv IN OUT EmpCurTyp) IS BEGIN OPEN emp_cv FOR SELECT * FROM employees; END open_emp_cv; END emp_data; /
DECLARE TYPE empcurtyp IS REF CURSOR; TYPE namelist IS TABLE OF employees.last_name%TYPE; TYPE sallist IS TABLE OF employees.salary%TYPE; emp_cv empcurtyp; names namelist; sals sallist; BEGIN OPEN emp_cv FOR SELECT last_name, salary FROM employees WHERE job_id = 'SA_REP'; FETCH emp_cv BULK COLLECT INTO names, sals; CLOSE emp_cv; -- loop through the names and sals collections FOR i IN names.FIRST .. names.LAST LOOP DBMS_OUTPUT.PUT_LINE('Name = ' || names(i) || ', salary = ' || sals(i)); END LOOP; END; /
1、不能再包说明中声明游标变量;
2、不能用“=”运算符比较游标变量相等性、不等性及是否为空;
3、不能存储于表列中;
4、不能将游标变量存在于关联数组、嵌套表或数组;
5、游标和游标变量之前是不可互操作的!
--------------------------------------------------------------------------------------
附:
------------------------
1、强类型游标:
CREATE OR REPLACE PACKAGE strongly_typed IS TYPE return_cur IS REF CURSOR RETURN all_tables%ROWTYPE; PROCEDURE child(p_return_rec OUT return_cur); PROCEDURE parent(p_NumRecs PLS_INTEGER); END strongly_typed; /
CREATE OR REPLACE PACKAGE BODY strongly_typed IS PROCEDURE child(p_return_rec OUT return_cur) IS BEGIN OPEN p_return_rec FOR SELECT * FROM all_tables; END child; --================================================== PROCEDURE parent (p_NumRecs PLS_INTEGER) IS p_retcur return_cur; at_rec all_tables%ROWTYPE; BEGIN child(p_retcur); FOR i IN 1 .. p_NumRecs LOOP FETCH p_retcur INTO at_rec; dbms_output.put_line(at_rec.table_name || ' - ' || at_rec.tablespace_name || ' - ' || TO_CHAR(at_rec.initial_extent) || ' - ' || TO_CHAR(at_rec.next_extent)); END LOOP; END parent; END strongly_typed; /
set serveroutput on exec strongly_typed.parent(1); exec strongly_typed.parent(8);
2、弱类型游标:
CREATE OR REPLACE PROCEDURE child ( p_NumRecs IN PLS_INTEGER, p_return_cur OUT SYS_REFCURSOR) IS BEGIN OPEN p_return_cur FOR 'SELECT * FROM all_tables WHERE rownum <= ' || p_NumRecs ; END child; / CREATE OR REPLACE PROCEDURE parent (pNumRecs VARCHAR2) IS p_retcur SYS_REFCURSOR; at_rec all_tables%ROWTYPE; BEGIN child(pNumRecs, p_retcur); FOR i IN 1 .. pNumRecs LOOP FETCH p_retcur INTO at_rec; dbms_output.put_line(at_rec.table_name || ' - ' || at_rec.tablespace_name || ' - ' || TO_CHAR(at_rec.initial_extent) || ' - ' || TO_CHAR(at_rec.next_extent)); END LOOP; END parent; / set serveroutput on exec parent(1); exec parent(17);
3、预定义游标变量:
CREATE TABLE employees ( empid NUMBER(5), empname VARCHAR2(30)); INSERT INTO employees (empid, empname) VALUES (1, 'Dan Morgan'); INSERT INTO employees (empid, empname) VALUES (2, 'Hans Forbrich'); INSERT INTO employees (empid, empname) VALUES (3, 'Caleb Small'); COMMIT; CREATE OR REPLACE PROCEDURE pass_ref_cur(p_cursor SYS_REFCURSOR) IS TYPE array_t IS TABLE OF VARCHAR2(4000) INDEX BY BINARY_INTEGER; rec_array array_t; BEGIN FETCH p_cursor BULK COLLECT INTO rec_array; FOR i IN rec_array.FIRST .. rec_array.LAST LOOP dbms_output.put_line(rec_array(i)); END LOOP; END pass_ref_cur; / set serveroutput on DECLARE rec_array SYS_REFCURSOR; BEGIN OPEN rec_array FOR 'SELECT empname FROM employees'; pass_ref_cur(rec_array); CLOSE rec_array; END; /
-----------------------------------------------------
Dylan presents.