IF NOT EXISTS 在函数 PLSQL 中
我有一个函数,它在打开游标之前具有三个 If/Then 语句.If/Then 语句在打开游标之前检查有效性.
I have a function which has three If/Then statements before opening a cursor. The If/Then statements check validity prior to opening the cursor.
我想再添加一个 If/Then 有效性检查,但是,它比其他的要复杂一些.下面是一个示例,我已经阻止评论了我想添加的内容:
I would like to add one more If/Then validity check, however, it is a bit more complicated than the others. Below is a sample, and I have block commented what I would like to add:
begin
if not procedure.validation_function (<variable>, <condition>=TRUE) then
return variable2;
end if;
/* if not exists
(
SELECT 'x' FROM table1
WHERE table1_id = variable1_id
AND trunc(sysdate) < trunc(table1_date + 60)
) then
return variable2;
end if; */
open cursor(<argument>);
fetch cursor into <variable>;
close cursor;
return <variable>;
end;
我的问题是我来自 T-SQL 世界,我发现在 PL/SQL 中 if not exists 命令不起作用.有没有办法可以从函数内部使用 If NO_DATA_FOUND 语句来使用 SELECT?
My problem is that I come from a T-SQL world, and I am finding in PL/SQL the if not exists command does not work. Is there a way I can, from within the function, have an If NO_DATA_FOUND statement where I utilize SELECT?
有没有办法在其中嵌套另一个函数,以便我可以:
Is there a way to nest another function within that, so I can:
begin
SELECT ....
FROM ....
WHERE ....
if NO_DATA_FOUND then
return variable2;
end if;
end;
推荐答案
Exists
条件只能在 SQL 语句中使用,不能在 PL/SQL 中直接使用.有几个选项:
Exists
condition can be used only in SQL statement, it cannot be used directly in PL/SQL. There are several options:
在
select
语句中使用case
表达式和exists
条件:
Using
case
expression withexists
condition inside aselect
statement:
SQL> declare
2 l_exists number(1);
3 begin
4 select case
5 when exists(select 1
6 from employees
7 where department_id = 1)
8 then 1
9 else 0
10 end into l_exists
11 from dual;
12
13 if (l_exists = 1)
14 then
15 dbms_output.put_line('exists');
16 else
17 dbms_output.put_line(q'[doesn't exist]');
18 end if;
19 end;
20 /
doesn't exist
PL/SQL procedure successfully completed
Or(需要rownum
,保证多条记录满足匹配条件,只返回一条记录):
Or (rownum
is needed to guarantee that the only one record will be returned if there are several records meet matching condition):
SQL> declare
2 l_exists number;
3 begin
4
5 select 1
6 into l_exists
7 from employees
8 where department_id = 100
9 and rownum = 1;
10
11 dbms_output.put_line('exists');
12
13 exception
14 when no_data_found
15 then dbms_output.put_line(q'[doesn't exist]');
16 end;
17 /
exists
PL/SQL procedure successfully completed
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