如何编写 PL/SQL 在插入之前先检查记录是否存在

Question

背景：我有桌子：

TUTPRAC： CLASSID、UNITCODE、STAFFNO、CLASSDAY、CLASSTIME、CLASSTYPE、ROOMNUM

UNITSTREAM： STREAMID、UNITCODE、STAFFNO、日期、时间、位置

问题：所以我有一个数据库和表，我试图创建一个函数，在打开一个新类之前检查一个类是否打开，这 程序必须确保两者之间没有任何重叠（在时间、日期或位置方面的冲突） 该特定单元的流（讲座），辅导课程和实践课程。 TUTPRACS 包含教程和实践的记录，而 UNITSTREAM 包含流（讲座）的记录。

我也希望程序也 引发一个名为 CLASS_OVERLAPS 的异常，在发生冲突时打印一条警报消息。

我对 PL/SQL 还很陌生，因此我们将不胜感激。

CREATE OR REPLACE PROCEDURE OPEN_CLASS(
           p_class IN TUTPRAC.CLASSID%TYPE,
           p_unitc IN TUTPRAC.UNITCODE%TYPE,
           p_classd IN TUTPRAC.CLASS_DAY%TYPE,
           p_classt IN TUTPRAC.CLASS_TIME%TYPE,
           p_classtp IN TUTPRAC.CLASS_TYPE%TYPE,
           p_roomnm IN TUTPRAC.ROOMNUM%TYPE)
    IS
    BEGIN

      INSERT INTO TUTPRAC ("CLASSID", "UNITCODE", "CLASS_DAY", "CLASS_TIME", "CLASS_TYPE", "ROOMNUM") 
      VALUES (p_class, p_unitc, p_classd, p_classt, p_classtp, p_roomnm);

      COMMIT;

    END;

Answer 1

你可以这样试试：

CREATE OR REPLACE PROCEDURE OPEN_CLASS(
           p_class IN TUTPRAC.CLASSID%TYPE,
           p_unitc IN TUTPRAC.UNITCODE%TYPE,
           p_classd IN TUTPRAC.CLASS_DAY%TYPE,
           p_classt IN TUTPRAC.CLASS_TIME%TYPE,
           p_classtp IN TUTPRAC.CLASS_TYPE%TYPE,
           p_roomnm IN TUTPRAC.ROOMNUM%TYPE)
    IS
    BEGIN

DECLARE
    x NUMBER:=0;
BEGIN
    -- checks
    SELECT nvl((SELECT 1 FROM TUTPRAC WHERE CLASSID = p_class and UNITCODE  = p_unitc and CLASS_DAY = p_classd and CLASS_TIME = p_classt and CLASS_TYPE = p_classtp and ROOMNUM = p_roomnm) , 0) INTO x FROM dual;

    -- insert
    IF (x = 1) THEN
        INSERT INTO TUTPRAC ("CLASSID", "UNITCODE", "CLASS_DAY", "CLASS_TIME", "CLASS_TYPE", "ROOMNUM") 
      VALUES (p_class, p_unitc, p_classd, p_classt, p_classtp, p_roomnm);
    END IF;

END;

或者你可以像这样使用 EXISTS：

    CREATE OR REPLACE PROCEDURE OPEN_CLASS(
               p_class IN TUTPRAC.CLASSID%TYPE,
               p_unitc IN TUTPRAC.UNITCODE%TYPE,
               p_classd IN TUTPRAC.CLASS_DAY%TYPE,
               p_classt IN TUTPRAC.CLASS_TIME%TYPE,
               p_classtp IN TUTPRAC.CLASS_TYPE%TYPE,
               p_roomnm IN TUTPRAC.ROOMNUM%TYPE)
        IS
        BEGIN

          INSERT INTO TUTPRAC ("CLASSID", "UNITCODE", "CLASS_DAY", "CLASS_TIME", "CLASS_TYPE", "ROOMNUM") 
INSERT INTO table
SELECT p_class, p_unitc, p_classd, p_classt, p_classtp, p_roomnm
  FROM dual 
 WHERE NOT EXISTS (SELECT NULL 
                     FROM TUTPRAC 
                    WHERE CLASSID = p_class and UNITCODE  = p_unitc and CLASS_DAY = p_classd and CLASS_TIME = p_classt and CLASS_TYPE = p_classtp and ROOMNUM = p_roomnm
                  )

Answer 2

你知道合并吗？ Merge

CREATE OR REPLACE 
PROCEDURE open_class(
           p_class IN TUTPRAC.CLASSID%TYPE,
           p_unitc IN TUTPRAC.UNITCODE%TYPE,
           p_classd IN TUTPRAC.CLASS_DAY%TYPE,
           p_classt IN TUTPRAC.CLASS_TIME%TYPE,
           p_classtp IN TUTPRAC.CLASS_TYPE%TYPE,
           p_roomnm IN TUTPRAC.ROOMNUM%TYPE)
    IS
    BEGIN
   merge into TUTPRAC a
   using (select p_class CLASSID,
                 p_unitc UNITCODE,
                 p_classd CLASS_DAY,
                 p_classt CLASS_TIME,
                 p_classtp CLASS_TYPE,
                 p_roomnm ROOMNUM from dual) b
      on (a.CLASSID = b.CLASSID
          and a.UNITCODE = b.UNITCODE
          and a.CLASS_DAY = b.CLASS_DAY
          and a.CLASS_TYPE = b.CLASS_TYPE
          and a.ROOMNUM = b.ROOMNUM)
   WHEN NOT MATCHED THEN INSERT (a.CLASSID ,a.UNITCODE, a.CLASS_DAY, a.CLASS_TYPE, a.ROOMNUM)
   values  ( b.CLASSID
          , b.UNITCODE
          , b.CLASS_DAY
          , b.CLASS_TYPE
          , b.ROOMNUM);
   if sql%ROWCOUNT = 0 then
    dbms_output.put_line('Class alredy exists');
   else
   dbms_output.put_line('Class added');
   end if;
  commit;
END;
/