PLS-00103 error while executing a sql block (Encountered the symbol "SELECT" ...)

Question

我正在尝试学习 PLSQL，这是我一直在尝试执行的代码，当我执行代码时出现以下错误。

ORA-06550: line 2, column 7:
PLS-00103: Encountered the symbol "SELECT" when expecting one of the following:

   ( - + case mod new not null <an identifier>
   <a double-quoted delimited-identifier> <a bind variable>
   continue avg count current exists max min prior sql stddev
   sum variance execute forall merge time timestamp interval
   date <a string literal with character set specification>
   <a number> <a single-quoted SQL string> pipe
   <an alternatively-quoted string literal with character set specification>
   <an alternat
ORA-06550: line 2, column 58:
PLS-00103: Encountered the symbol ")" when expecting one of the following:

   * & - + ; / at for mod remainder rem <an exponent (**)> and
   or group having intersect minus order start union where
   connect || multiset

我知道你可以给select语句赋一个变量，然后在IF语句中使用那个变量，我只想知道下面代码中的错误。

BEGIN
  IF((SELECT marks FROM students WHERE student_id ='s10')= 'Passed') THEN
        DBMS_OUTPUT.PUT_LINE('Hello!');
  END IF;
END;

Answer 1

begin 
for i in (SELECT marks FROM students WHERE student_id ='s10') loop
    if i.marks = 'Passed' then 
        DBMS_OUTPUT.PUT_LINE('Hello!');
    end if;
end loop;
end;

OR 如果 student_id 是唯一的

declare
v_mark students.marks%type;
begin 
SELECT marks into v_mark FROM students WHERE student_id ='s10';
    if v_mark = 'Passed' then 
        DBMS_OUTPUT.PUT_LINE('Hello!');
    end if;
end;

Answer 2

使用光标：

declare
cursor c1 is SELECT marks FROM students WHERE student_id ='s10';
begin
for r1 in c1 loop
    if r1.marks = 'Passed' then 
        DBMS_OUTPUT.PUT_LINE('Hello!');
    end if; 
end loop; 
end;

PLS-00103 error while executing a sql block (Encountered the symbol "SELECT" ...)

PLS-00103 error while executing a sql block (Encountered the symbol "SELECT" ...)

sql

oracle

plsql