Oracle 此函数用于计算两个日期之间的假期数，有什么问题？

我不熟悉创建Oracle函数。这个函数有什么问题

create or replace
FUNCTION count_holidays(
      t_date DATE,
      p_date DATE)
    RETURN NUMBER
  IS
    return_dt NUMBER;
  BEGIN
    SELECT COUNT(DISTINCT dated)
    FROM holiday_new
    WHERE TRUNC(dated)     IN
      (SELECT TRUNC(t_date) + level - 1 
      from dual
        CONNECT BY level <= TRUNC(p_date)-TRUNC(t_date) + 1
      )
    INTO return_dt
    FROM dual;
    RETURN return_dt;
  END;

错误：

错误9,5:PL/SQL:SQL语句被忽略 错误16,5:PL/SQL:ORA-00933:SQL命令未正确结束

此查询错误：

SELECT COUNT(DISTINCT dated)
FROM holiday_new
WHERE TRUNC(dated) IN
  (    SELECT TRUNC(t_date) + level - 1 
       from dual
       CONNECT BY level <= TRUNC(p_date)-TRUNC(t_date) + 1
  )
INTO return_dt
FROM dual;

我猜这个查询应该是这样的：

SELECT COUNT(DISTINCT dated) INTO return_dt
FROM holiday_new
WHERE TRUNC(dated) IN
  (    SELECT TRUNC(t_date) + level - 1 
       from dual
       CONNECT BY level <= TRUNC(p_date)-TRUNC(t_date) + 1
  );

这是一种非常低效的方法来选择带有某些日期的记录，我将使用以下查询：

SELECT COUNT(DISTINCT dated) INTO return_dt
FROM holiday_new
WHERE dated >= trunc(t_date) AND dated < trunc(p_date + 1);

此查询错误：

SELECT COUNT(DISTINCT dated)
FROM holiday_new
WHERE TRUNC(dated) IN
  (    SELECT TRUNC(t_date) + level - 1 
       from dual
       CONNECT BY level <= TRUNC(p_date)-TRUNC(t_date) + 1
  )
INTO return_dt
FROM dual;

我猜这个查询应该是这样的：

SELECT COUNT(DISTINCT dated) INTO return_dt
FROM holiday_new
WHERE TRUNC(dated) IN
  (    SELECT TRUNC(t_date) + level - 1 
       from dual
       CONNECT BY level <= TRUNC(p_date)-TRUNC(t_date) + 1
  );

这是一种非常低效的方法来选择带有某些日期的记录，我将使用以下查询：

SELECT COUNT(DISTINCT dated) INTO return_dt
FROM holiday_new
WHERE dated >= trunc(t_date) AND dated < trunc(p_date + 1);