plsql - PL/SQL 检查查询是否返回空

Question

我正在编写一个过程，我需要检查我的选择查询是否返回空记录。
(在这个例子中是否没有 x,y 架子)

我怎样才能做到这一点？

我试过这个:

temp shelves.loadability%TYPE := NULL;
BEGIN

select loadability into temp from shelves where rownumber = x and columnnumber = y;
IF temp IS NOT NULL THEN
/* do something when it's not empty */
ELSE
/* do the other thing when it's empty */
END IF;

但是 if 的第二个分支永远不起作用......

编辑:

哦，原来如此简单...

temp shelves.loadability%TYPE;
BEGIN

select count(*) into temp from shelves where rownumber = x and columnnumber = y;
IF temp != 0 THEN
/* do something when it's not empty */
ELSE
/* do the other thing when it's empty */
END IF;

END;

Answer 1

使用异常处理程序

Begin
  select column
  into variable
  from table
  where ...;

  -- Do something with your variable

exception
 when no_data_found then
    -- Your query returned no rows --

 when too_many_rows
    -- Your query returned more than 1 row --

end;