是否可以将sql％rowcount用于SELECT? [英] Is it possible to use sql%rowcount for SELECT?

问题描述

下面的代码可能返回多个行. sql%rowcount会返回获取的行数吗?

The code below may return more than one row. Will sql%rowcount return the number of rows fetched?

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

这是我的示例处理；我是否以正确的方式使用sql%rowcount?

This is my sample proc; am I using sql%rowcount in correct way?

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;

推荐答案

根据您的评论

如果第二个选择"查询返回多个行，我想获取第一行并进行处理

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

...这应该可行，但可能不符合您的期望，因为您尚未定义第一个"的含义.

... this ought to work, but perhaps not quite as you expect, as you haven't defined what the 'first one' means.

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';

    -- 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, STATIC_IP into outport, 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;

---

exception处理程序适用于整个块.如果任何select语句均未找到任何行，则no_data_found异常将由该块处理，并将outretvalue设置为-12.

---

The exception handler applies to the whole block. If any of the select statements find no rows, the no_data_found exception will be handled by that block and will set outretvalue to -12.

如果每个select都希望使用不同的outretvalue，则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:

If you want a different outretvalue for each select then you can wrap them in sub-blocks, each with their own exception handling section:

CREATE PROCEDURE Procn(in_Hid IN VARCHAR2, outInststatus OUT VARCHAR2,
    outSockid IN NUMBER, outport OUT VARCHAR2, outIP OUT 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, STATIC_IP into outport, 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;

仅在调用方需要知道哪个select失败的情况下才需要这样做，并且如果您从未真正期望它们中的任何一个失败，则可能更常见的是根本不捕获异常并让调用方看到raw no_data_found并决定要怎么做.但这取决于异常条件对您和您的应用程序意味着什么.

You only need to do that if the caller needs to know which select failed, and if you never really expect any of them to fail then it's probably more common not to catch the exception at all and let the caller see the raw no_data_found and decide what to do. Depends what the exception condition means to you and your application though.

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