sql - 检查 SYS_REFCURSOR 是否为空的最佳方法

Question

我有一个带有来自选择的值的游标，我想根据我是否找到任何行来做一些事情。

recs_Table SYS_REFCURSOR;

begin

    open recs_Table for
       select * from table1, table2;


    if recs_Table%found then
        --do this
    else
        --do that
    end if;

end;

这似乎不起作用，有什么帮助吗？

Answer 1

You need to execute a FETCH against the cursor prior to using the %FOUND attribute. Change your code to something like

DECLARE
  recs_Table SYS_REFCURSOR;
  nTable_1_value  NUMBER;
  nTable_2_value  NUMBER;
begin

    open recs_Table for
       select * from table1, table2;


    FETCH recs_Table INTO nTable_1_value, nTable_2_value;

    if recs_Table%found then
        --do this
    else
        --do that
    end if;

end;

Note that the way you'll probably need to add variables to the INTO clause of the FETCH statement, one for each column in TABLE1 and TABLE2. Note also that the way this cursor is written you'll probably get more rows returned than you might expect; because there is no join criteria specified you'll get what's called a Cartesian join, where each row in TABLE1 is joined to each row in TABLE2 - thus, the number of rows you'll get back is (# of rows in TABLE1) * (# of rows in TABLE2).

A potentially simpler way to do this would be to use a cursor FOR loop, as follows:

DECLARE
  bData_found  BOOLEAN := FALSE;
begin
  FOR aRow IN (select * from table1, table2)
  LOOP
    -- If the program gets here, it means a row was fetched

    -- do this

    bData_found := TRUE;

    EXIT;  -- if you only care if data was found and don't want to 
           -- process all the rows
  END LOOP;

  IF NOT bData_found THEN
    -- do that
  END IF;
end;

Share and enjoy.

Answer 2

我们使用两个程序来执行结果

create or replace procedure pro_sample(recs_Table out SYS_REFCURSOR) is

    begin
       open recs_Table for
           select * from table1, table2;
    end;

上述过程将用于打开游标

create or replace procedure pro_sample(recs_Table out SYS_REFCURSOR) is
   sam sys_refcursor;
   var number;
              -- if you have any variables then declare them
  begin
    pro_sample(sam);
    fetch sam into var;
    if sam%found then
       --do this
        else
       --do that
    end if;
    close sam;
 end;

上述过程将帮助您了解游标是否包含行

Answer 3

这对我有用：D

    IF(MYCURSOR%ROWCOUNT = 0)THEN
         DO SOMETHING ...
    ENDIF;

Answer 4

create or replace procedure pro_sample(recs_Table out SYS_REFCURSOR) is
    begin
       open recs_Table for
           select a,b,c,d from table1, table2;
    end;

create or replace function haveRows_pro_sample is
sam sys_refcursor;
var varchar(200);
varOut number:=0;
    begin
        pro_sample(sam);
        fetch sam into var,var,var,var;   
        if sam%found then
          varOut :=1;
        end if;
        return varOut;
    end;

Answer 5

您还可以通过select count()在打开游标之前执行查询然后检查它来选择变量的计数，如下所示：

select count(*) into v_count from table1;
if v_count>0 then
    --do this
    open my_cursor for 
        select var1,var2,var3 from table1;
    fetch etc.
else
    --do that
end if;