oracle 函數檢查兩個表的記錄

Question

我想在 oracle 11g 中編寫下面的函數，並且我嘗試了很多語法，但它們都不起作用。

function a(id Number) return VARCHAR2
begin

return(
case 
when
check if record exists in first table 
then
select a varchar column from record
when
check if record exists in second table 
then
select a varchar column from record
else
 ''
end
)

end

有什么建議 ？

Answer 1

這是一種選擇。 我使用了 Scott 的示例表。 閱讀代碼中的注釋。

SQL> create or replace function f_test (par_id number)
  2    return varchar2
  3  is
  4    l_rec_emp   emp%rowtype;
  5    l_rec_dept  dept%rowtype;
  6    retval      varchar2(20);
  7  begin
  8    begin
  9      -- select from the first table
 10      select *
 11        into l_rec_emp
 12        from emp
 13        where empno = par_id;
 14      -- something was found; set return value
 15      retval := l_rec_emp.ename;
 16    exception
 17      when no_data_found then
 18      -- nothing was found in the first table; go on to the second
 19      begin
 20        select *
 21          into l_rec_dept
 22          from dept
 23          where deptno = par_id;
 24        -- something was found; set return value
 25        retval := l_rec_dept.dname;
 26      exception
 27        when no_data_found then
 28        -- nothing was found in the second table; return a dummy value
 29        retval := 'Dummy';
 30      end;
 31    end;
 32    -- return what you've found
 33    return retval;
 34  end;
 35  /

Function created.

我要測試的數據是

SQL> select empno, ename from emp where empno = 7369;

     EMPNO ENAME
---------- ----------
      7369 SMITH

SQL> select deptno, dname from dept where deptno = 10;

    DEPTNO DNAME
---------- --------------
        10 ACCOUNTING

SQL> select f_test(7369) retval_1,
  2         f_test(10)   retval_2,
  3         f_test(-1)   retval_3
  4  from dual;

RETVAL_1     RETVAL_2     RETVAL_3
------------ ------------ ------------
SMITH        ACCOUNTING   Dummy

SQL>