Oracle遊標

--顯式遊標---------------------------------------------------------//   
--001  
DECLARE   
    CURSOR c1 IS  --聲明遊標   
        SELECT name,address FROM student ORDER BY name;   
    v_name student.name%TYPE;   
    v_addr student.address%TYPE;   
BEGIN   
    OPEN c1;  --打開遊標   
    FETCH c1 INTO v_name,v_addr;  --第一次定位讀取數據，並保存在變量   
    --循環讀取數據   
    WHILE c1%FOUND LOOP   
        DBMS_OUTPUT.PUT_LINE(TO_CHAR(c1%ROWCOUNT) || '  ' || v_name || ' , ' || v_addr);   
        FETCH c1 INTO v_name,v_addr;   
    END LOOP;   
    DBMS_OUTPUT.PUT_LINE('Total rows is : ' || c1%ROWCOUNT);   
    CLOSE c1;  --關閉遊標   
END;   
/   
--002  
DECLARE   
    CURSOR cur_emp IS   
        SELECT sal FROM emp WHERE deptno = 20 FOR UPDATE OF sal;   
    v_sal emp.sal%TYPE;   
BEGIN   
    OPEN cur_emp;   
    FETCH cur_emp INTO v_sal;   
    LOOP   
        EXIT WHEN cur_emp%NOTFOUND;   
        IF v_sal < 2000 THEN   
            UPDATE emp SET sal = 2000 WHERE current OF cur_emp;  --更新當前數據   
        END IF;   
        FETCH cur_emp INTO v_sal;   
    END LOOP;   
    DBMS_OUTPUT.PUT_LINE('命令執行完畢');   
       
    IF cur_emp%ISOPEN THEN   
        CLOSE cur_emp;   
        IF cur_emp%ISOPEN THEN   
            DBMS_OUTPUT.PUT_LINE('Cursor state : Open');   
            CLOSE cur_emp;   
        ELSE   
            DBMS_OUTPUT.PUT_LINE('Cursor state : Close');   
        END IF;   
    END IF;   
END;   
/   
  
--隱式遊標---------------------------------------------------------//   
--不能顯式的使用OPEN、CLOSE和FETCH語句，他會自動完成   
DECLARE   
    no   emp.empno%TYPE;   
    name emp.ename%TYPE;       
BEGIN   
    SELECT empno,ename INTO no,name FROM emp WHERE empno = '7788';   
    IF SQL%ISOPEN THEN   
        DBMS_OUTPUT.PUT_LINE('Cursor state : Open');   
    ELSE   
        DBMS_OUTPUT.PUT_LINE('Cursor state : Close');   
    END IF;   
    DBMS_OUTPUT.PUT_LINE(no || '    ' || name);   
    DBMS_OUTPUT.PUT_LINE('Return rows : ' || SQL%ROWCOUNT);   
EXCEPTION   
    WHEN CURSOR_ALREADY_OPEN THEN   
        DBMS_OUTPUT.PUT_LINE('Cursor already open');   
    WHEN NO_DATA_FOUND THEN   
        DBMS_OUTPUT.PUT_LINE('No data found');   
    WHEN TOO_MANY_ROWS THEN   
        DBMS_OUTPUT.PUT_LINE('Return many rows');   
END;   
/   
  
--遊標變量（一個遊標變量可以在一個PL\SQL塊中使用多次）---------------------------//   
DECLARE   
    TYPE refcur IS REF CURSOR;  --[RETURN TYPE]   
    cur_emp refcur;  --引用遊標   
    dept emp.deptno%TYPE;   
    name emp.ename%TYPE;   
BEGIN   
    OPEN cur_emp FOR SELECT deptno FROM emp WHERE empno = '7788';   
    FETCH cur_emp INTO dept;   
    DBMS_OUTPUT.PUT_LINE('Dept : ' || dept);   
    CLOSE cur_emp;   
  
    OPEN cur_emp FOR SELECT ename FROM emp WHERE empno = '7788';   
    FETCH cur_emp INTO name;   
    DBMS_OUTPUT.PUT_LINE('Name : ' || name);   
    CLOSE cur_emp;   
END;   
/   
  
--遊標在三種循環中的使用-------------------------------------------//   
--001--Loop   
DECLARE   
    CURSOR cur_emp IS   
        SELECT ename FROM emp;   
    v_name emp.ename%TYPE;   
BEGIN   
    OPEN cur_emp;   
    FETCH cur_emp INTO v_name;   
    LOOP   
        EXIT WHEN cur_emp%NOTFOUND;   
        DBMS_OUTPUT.PUT_LINE('Name is : ' || v_name);   
        FETCH cur_emp INTO v_name;   
    END LOOP;   
    DBMS_OUTPUT.PUT_LINE('Return rows : ' || cur_emp%ROWCOUNT);   
    CLOSE cur_emp;   
END;   
/   
--002--While   
DECLARE   
    CURSOR cur_emp IS   
        SELECT ename FROM emp;   
    v_name emp.ename%TYPE;   
BEGIN   
    OPEN cur_emp;   
    FETCH cur_emp INTO v_name;   
    WHILE cur_emp%FOUND LOOP   
        DBMS_OUTPUT.PUT_LINE('Name is : ' || v_name);   
        FETCH cur_emp INTO v_name;   
    END LOOP;   
    DBMS_OUTPUT.PUT_LINE('Return rows : ' || cur_emp%ROWCOUNT);   
    CLOSE cur_emp;   
END;   
/   
--003--For   
--注：在使用 FOR 循環時，不能顯式的使用 open、colse 和 FETCH 語句，他會自動完成   
DECLARE   
    rows number := 0;   
    CURSOR cur_emp IS   
        SELECT ename FROM emp;   
BEGIN   
    FOR v_emp in cur_emp LOOP   
        DBMS_OUTPUT.PUT_LINE('name is : ' || v_emp.ename);   
        rows := rows + 1;   
    END LOOP;   
    DBMS_OUTPUT.PUT_LINE('Return rows : ' || rows);   
END;   
/