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[英]How to use a rowcount in select statement to modify the query to fetch data for 10 days , if rowcount is 0 for 5 days?
[英]Is it possible to use sql%rowcount for SELECT?
下面的代码可能会返回多行。 请问sql%rowcount
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;
是的,您可以使用SQL%ROWCOUNT
。 它在PL / SQL中有效。
但是,在PL / SQL中,查询的结果需要转移到某个PL / SQL表中。 PL / SQL永远不会将结果发送到输出 (终端,窗口等)。 所以SELECT * FROM
不起作用。
您的代码可能如下所示:
DECLARE
TYPE emp_t ...;
emp_tab emp_t;
BEGIN
SELECT *
BULK COLLECT INTO emp_tab
FROM emp
WHERE empname = 'Justin' AND dept='IT';
IF sql%rowcount > 0 THEN
.. do something ...
END IF;
END;
/
更新 :
更新的问题表明您正在寻找其他东西。
选项1:使用例外
如果有0行或多于1行,则这些情况将单独处理(作为错误):
BEGIN
select PORT_NUMBER,STATIC_IP into outport, outIP
from TINST
where INST_ID = in_Hid AND IP_PORT_STATUS = 'Y';
EXCEPTION
WHEN NO_DATA_FOUND THEN
outretvalue := -12;
RETURN;
WHEN TOO_MANY_ROWS THEN
outretvalue := -13;
RETURN;
END;
选项2:使用聚合
使用聚合,查询将始终返回一行。 如果现在源行与WHERE子句匹配,则两个结果值都将为NULL。 如果WHERE子句匹配多行,则将采用最大值。
请注意,此查询可能会返回端口号和最初不在同一行的IP地址。
select MAX(PORT_NUMBER), MAX(STATIC_IP) into outport, outIP
from TINST
where INST_ID = in_Hid AND IP_PORT_STATUS = 'Y';
IF outport IS NULL OR outIP IS NULL THEN
outretvalue := -12;
RETURN;
END IF;
选项3:使用ROWNUM
此查询最多返回一行。 如果没有与WHERE子句匹配的行,则抛出异常并需要处理:
BEGIN
select PORT_NUMBER, STATIC_IP into outport, outIP
from TINST
where INST_ID = in_Hid AND IP_PORT_STATUS = 'Y'
AND ROWNUM = 1;
EXCEPTION
WHEN NO_DATA_FOUND THEN
outretvalue := -12;
RETURN;
END;
根据您的评论
如果第二个'select'查询返回多行,我想取第一个并用它处理
......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, 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
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, 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;
如果调用者需要知道哪个select
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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