oracle – 是否可以使用sql％rowcount进行SELECT？

下面的代码可能会返回多行.请问sql％rowcount是否返回获取的行数？

select * from emp where empname = 'Justin' and dept='IT'
if sql%rowcount>0
    ...

这是我的样本过程;我以正确的方式使用sql％rowcount吗？

CREATE PROCEDURE Procn(in_Hid IN VARCHAR2,outInststatus OUT VARCHAR2,outSockid IN NUMBER,outport OUT VARCHAR2,outIP OUT VARCHAR2,outretvalue OUT NUMBER)
AS
BEGIN
select INST_STATUS into outInststatus from TINST_child where INST_ID = in_Hid and INST_STATUS = 'Y';
if outInststatus = 'Y' then 
     select PORT_NUMBER,STATIC_IP into outport,outIP from TINST where INST_ID = in_Hid and IP_PORT_STATUS = 'Y';
    if sql%rowcount >= 1 then
       select SOCK_ID into outSockid from TINST where PORT_NUMBER = outport AND STATIC_IP = outIP;  
       outretvalue := 0;
    else
       outretvalue := -12;
    end if;
  EXCEPTION
  WHEN NO_DATA_FOUND THEN
   outretvalue := -13;
end if;
END;

解决方法

If 2nd ‘select’ query returns more than one row i want to take the first one and process with it

……这应该有效,但也许并不像你期望的那样,因为你没有定义“第一个”的含义.

CREATE PROCEDURE Procn(in_Hid IN VARCHAR2,outretvalue OUT NUMBER)
AS
BEGIN
    select INST_STATUS into outInststatus
    from TINST_child
    where INST_ID = in_Hid and INST_STATUS = 'Y';

    -- no need to check if outInstatus is Y,that's all it can be here

    -- restricting with `rownum` means you'll get at most one row,so you will
    -- not get too_many_rows. But it will be an arbitrary row - you have no
    -- criteria to determine which of the multiple rows you want. And you can
    -- still get no_data_found which will go to the same exception and set -12
    select PORT_NUMBER,outIP
    from TINST
    where INST_ID = in_Hid and IP_PORT_STATUS = 'Y'
    and rownum < 2;

    -- no need to check sql%rowcount; it can only be 1 here

    -- not clear if this can return multiple rows too,and what should happen
    -- if it can; could use rownum restriction but with the same caveats
    select SOCK_ID into outSockid
    from TINST
    where PORT_NUMBER = outport AND STATIC_IP = outIP;   

    outretvalue := 0;
EXCEPTION
    WHEN NO_DATA_FOUND THEN
        outretvalue := -12;
END;

异常处理程序适用于整个block.如果任何select语句没有找到任何行,则no_data_found异常将由该块处理,并将outretvalue设置为-12.

如果你想为每个select选择不同的outretvalue,那么你可以将它们包装在子块中,每个子块都有自己的异常处理部分：

CREATE PROCEDURE Procn(in_Hid IN VARCHAR2,outretvalue OUT NUMBER)
AS
BEGIN
    BEGIN
        select INST_STATUS into outInststatus
        from TINST_child
        where INST_ID = in_Hid and INST_STATUS = 'Y';
    EXCEPTION
        WHEN NO_DATA_FOUND THEN
            outretvalue := -12;
    END;

    BEGIN
        select PORT_NUMBER,outIP
        from TINST
        where INST_ID = in_Hid and IP_PORT_STATUS = 'Y'
        and rownum < 2;
    EXCEPTION
        WHEN NO_DATA_FOUND THEN
            outretvalue := -13;
    END;

    BEGIN
        select SOCK_ID into outSockid
        from TINST
        where PORT_NUMBER = outport AND STATIC_IP = outIP;   
    EXCEPTION
        WHEN NO_DATA_FOUND THEN
            outretvalue := -14;
    END;

    outretvalue := 0;
END;

如果调用者需要知道哪个选择失败,你只需要这样做,如果你真的没有想到它们中的任何一个失败那么可能更常见的是根本不捕获异常并让调用者看到原始的no_data_found并决定什么去做.取决于异常条件对您和您的应用程序的意义.

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