在cursor FOR LOOP中使用游标属性

Question

我正在Scott模式中运行以下内容：

SET serveroutput ON;
BEGIN
FOR c_Emp IN (SELECT * FROM emp)
LOOP
dbms_output.put_line('The record processed by the cursor ' || c_Emp%rowcount);
END LOOP;
end;

这给出了错误：

游标属性不能应用于非游标"C_EMP"

然而，如果这是使用显式光标完成的，它可以很好地工作：

将serveroutput设置为打开；

DECLARE 
       emp_record emp%ROWTYPE; 
       count_variable NUMBER;
       CURSOR c IS 
SELECT * FROM emp;
BEGIN
OPEN c;
loop
fetch  c INTO emp_record;
exit WHEN c%notfound;
dbms_output.put_line ('The record count is   ' || c%rowcount);
END loop;
close c;
end;

只想了解：在使用CURSOR FOR LOOP时，索引变量是否不是游标属性，如果是，为什么？有人能解释一下吗。。。。

Answer 1

c_Emp不是光标，它是SELECT语句中每列都有字段的记录

c_Emp类似于第二个示例中的emp_record。

Answer 2

即使在使用FOR循环时，也必须显式定义光标。带有光标的FOR循环示例如下：

declare
 cursor c1 is select a from table;
begin
 FOR b in c1
 loop
  <required logic>
 end loop;
end;

Answer 3

要在for循环中获取索引，可以在隐式游标的select子句中添加rownum伪列。

SET serveroutput ON;
BEGIN
  FOR c_Emp IN (SELECT e.*, rownum FROM emp e)
  LOOP
    dbms_output.put_line('The record processed by the cursor ' || c_Emp.rownum);
  END LOOP;
end;

Answer 4

试试这个：

SET serveroutput ON;
DECLARE
x NUMBER :=0 ;
BEGIN
FOR c_Emp IN (SELECT * FROM emp)
LOOP
x := x+1;
dbms_output.put_line('The record processed by the cursor ' || x);
END LOOP;
-----
IF x>0 THEN
dbms_output.put_line('Cursr was opened');
ELSE
dbms_output.put_line('Cursr was not opened');
END IF; 
end;

Answer 5

SQL> create table product(
  2     product_id number(4)     not null,
  3     product_description varchar2(20) not null
  4  );
Table created.
SQL>
SQL> insert into product values (1,'Java');
1 row created.
SQL> insert into product values (2,'Oracle');
1 row created.
SQL> insert into product values (3,'C#');
1 row created.
SQL> insert into product values (4,'Javascript');
1 row created.
SQL> insert into product values (5,'Python');
1 row created.

SQL> create table company(
  2     product_id        number(4)    not null,
  3     company_id          NUMBER(8)    not null,
  4     company_short_name  varchar2(30) not null,
  5     company_long_name   varchar2(60)
  6  );
Table created.
SQL> insert into company values(1,1001,'A Inc.','Long Name A Inc.');
1 row created.
SQL> insert into company values(1,1002,'B Inc.','Long Name B Inc.');
1 row created.
SQL> insert into company values(1,1003,'C Inc.','Long Name C Inc.');
1 row created.
SQL> insert into company values(2,1004,'D Inc.','Long Name D Inc.');
1 row created.
SQL> insert into company values(2,1005,'E Inc.','Long Name E Inc.');
1 row created.
SQL> insert into company values(2,1006,'F Inc.','Long Name F Inc.');
1 row created.

SQL> DECLARE
  2    CURSOR cursorValue IS
  3      SELECT h.product_description,o.company_short_name FROM company o,product h
  4      WHERE o.product_id =h.product_id
  5      ORDER by 2;
  6    num_total_rows NUMBER;
  7  BEGIN
  8
  9    FOR idx IN cursorValue LOOP
 10      dbms_output.put_line(rpad(idx.product_description,20,' ')||' '||
 11      rpad(idx.company_short_name,30,' '));
 12
 13      num_total_rows :=cursorValue%ROWCOUNT;
 14    END LOOP;
 15    IF num_total_rows >0 THEN
 16      dbms_output.new_line;
 17      dbms_output.put_line('Total Organizations = '||to_char(num_total_rows));
 18    END IF;
 19  END;
 20  /
Java                 A Inc.
Java                 B Inc.
Java                 C Inc.
Oracle               D Inc.
Oracle               E Inc.
Oracle               F Inc.
Total Organizations = 6
PL/SQL procedure successfully completed.

SQL> drop table product;
Table dropped.

SQL> drop table company;
Table dropped.
    enter code here