使用动态表名称的oracle函数和游标 [英] oracle function and cursor using dynamic table name

问题描述

在我的oracle数据库中，我想使用游标创建一个函数或过程，该函数或过程将使用动态表名.这是我的代码.

IN my oracle database i want to create a function or procedure with cursor which will use dynamic table name.here is my code.

CREATE OR REPLACE Function Findposition ( model_in IN varchar2,model_id IN number) RETURN number IS cnumber number;
TYPE c1 IS REF CURSOR;
c2 c1;
BEGIN
open c2 FOR 'SELECT id,ROW_NUMBER() OVER ( ORDER BY id) AS rownumber FROM '||model_in;
FOR employee_rec in c2
LOOP
    IF employee_rec.id=model_id then
    cnumber :=employee_rec.rownumber;
    end if;
END LOOP;
close c2;
RETURN cnumber;
END;

帮助我解决此问题.IN

help me to solve this problem.IN

推荐答案

• 对于弱类型的引用游标，无需声明c1类型.您可以只使用SYS_REFCURSOR类型.
• 您不能像这样混合使用隐式和显式游标调用.如果要转到游标OPEN，则必须循环地从游标中移出FETCH，并且必须将其移至CLOSE.您不能OPEN和CLOSE它，但是在隐式游标循环中从中获取它.
• 您必须声明一个或多个变量才能将数据提取到其中.我声明了一个记录类型和该记录的一个实例，但是您可以轻松地在两个变量中声明两个局部变量和FETCH.
• ROWID是保留字，所以我改用ROWPOS.
• There is no need to declare a c1 type for a weakly typed ref cursor. You can just use the SYS_REFCURSOR type.
• You can't mix implicit and explicit cursor calls like this. If you are going to OPEN a cursor, you have to FETCH from it in a loop and you have to CLOSE it. You can't OPEN and CLOSE it but then fetch from it in an implicit cursor loop.
• You'll have to declare a variable (or variables) to fetch the data into. I declared a record type and an instance of that record but you could just as easily declare two local variables and FETCH into those variables.
• ROWID is a reserved word so I used ROWPOS instead.

将它们放在一起，您可以编写类似的内容

Putting that together, you can write something like

SQL> ed
Wrote file afiedt.buf

  1  CREATE OR REPLACE Function Findposition (
  2      model_in IN varchar2,
  3      model_id IN number)
  4    RETURN number
  5  IS
  6    cnumber number;
  7    c2      sys_refcursor;
  8    type result_rec is record (
  9      id      number,
 10      rowpos  number
 11    );
 12    l_result_rec result_rec;
 13  BEGIN
 14    open c2 FOR 'SELECT id,ROW_NUMBER() OVER ( ORDER BY id) AS rowpos FROM '||model_in;
 15    loop
 16      fetch c2 into l_result_rec;
 17      exit when c2%notfound;
 18      IF l_result_rec.id=model_id
 19      then
 20        cnumber :=l_result_rec.rowpos;
 21      end if;
 22    END LOOP;
 23    close c2;
 24    RETURN cnumber;
 25* END;
SQL> /

Function created.

我相信这会返回您期望的结果

I believe this returns the result you expect

SQL> create table foo( id number );

Table created.

SQL> insert into foo
  2    select level * 2
  3      from dual
  4   connect by level <= 10;

10 rows created.

SQL> select findposition( 'FOO', 8 )
  2    from dual;

FINDPOSITION('FOO',8)
---------------------
                    4

请注意，从效率的角度来看，最好将其编写为单个SQL语句，而不是每次打开一个游标并从表中获取每一行.如果确定要使用游标，则希望在找到感兴趣的行时退出游标，而不是继续从表中获取每一行.

Note that from an efficiency standpoint, you'd be much better off writing this as a single SQL statement rather than opening a cursor and fetching every row from the table every time. If you are determined to use a cursor, you'd want to exit the cursor when you've found the row you're interested in rather than continuing to fetch every row from the table.

从代码清晰的角度来看，许多变量名称和数据类型似乎很奇怪.您的参数名称似乎选择不当-例如，我不希望model_in是输入表的名称.声明名为c2的游标也是有问题的，因为它是非描述性的.

From a code clarity standpoint, many of your variable names and data types seem rather odd. Your parameter names seem poorly chosen-- I would not expect model_in to be the name of the input table, for example. Declaring a cursor named c2 is also problematic since it is very non-descriptive.

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