PL/SQL 检查查询是否返回空 [英] PL/SQL check if query returns empty

问题描述

我正在编写一个程序，我需要检查我的选择查询是否返回了空记录.(本例中是否没有x,y架子)

I'm writing a procedure, and i need to check whether my select query returned an empty record or not. (In this example whether there is no x,y shelf)

我该怎么做?

我试过了:

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...

But the second branch of the if never works...

哦，太简单了...

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;

推荐答案

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;

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