oracle - 从 PL/SQL 函数返回多个值

Question

我需要尝试在飞机上找到一个空闲座位，然后预订该座位。

我需要返回一个指示成功与否的值以及一个座位号。通过环顾四周，我发现函数不能返回超过 1 个值，因此我考虑使用数组，但查看这些文档后发现，我对 PL/SQL 的了解还不够好，无法理解如何使用它们.

所以我在这里，被困了。

到目前为止我得到的代码如下所示:

CREATE OR REPLACE FUNCTION RESERVE_SEAT(P_NO VARCHAR2, ID NUMBER, RESERVE_TIME NUMBER, S_NO VARCHAR2)
RETURN INTEGER AS
  RES INTEGER := 0;
  COUNTS INTEGER := 0;
BEGIN
SELECT COUNT(*) INTO COUNTS FROM SEAT WHERE SEAT_NO=S_NO AND PLANE_NO=P_NO;
IF(COUNTS = 1) THEN
  UPDATE SEAT
  SET RESERVED = ID, BOOKING_TIME = RESERVE_TIME, BOOKED=ID
  WHERE PLANE_NO=P_NO AND SEAT_NO=S_NO;
  COMMIT;
    ELSE IF(COUNTS = 0) THEN
      RES := -1;
    END IF;
  END IF;
  RETURN RES;
END RESERVE_SEAT;

上面的函数被下面的函数调用

CREATE OR REPLACE FUNCTION GET_FREE_SEAT(P_NO VARCHAR2, ID NUMBER, RESERVE_TIME NUMBER)
RETURN INTEGER AS
  RESERVED_SEAT_NO VARCHAR2(100) := 'NULL';
  RES INTEGER := 0; -- Assume Success Scenario from the Get-go
BEGIN
  SELECT SEAT_NO INTO RESERVED_SEAT_NO
  FROM SEAT
  WHERE RESERVED IS NULL AND BOOKED IS NULL AND ROWNUM = 1
  OR BOOKED IS NULL AND ((RESERVE_TIME - 5000) <= BOOKING_TIME) AND ROWNUM = 1;

  IF(RESERVED_SEAT_NO != 'NULL') THEN
    RES := RESERVE_SEAT(P_NO,ID,RESERVE_TIME,RESERVEd_SEAT_NO);
  END IF;
  RETURN RES;
END GET_FREE_SEAT;

现在不太确定该怎么做。

如何同时返回 RES 和 RESERVED_SEAT_NO ？

Answer 1

你不可能返回 2 个变量。必须是一个。

您可以使用可以从函数返回的自定义记录类型或数组。

TYPE new_type is record(RES pls_integer, RESERVED_SEAT_NO pls_integer);

CREATE OR REPLACE FUNCTION GET_FREE_SEAT(P_NO VARCHAR2, ID NUMBER, RESERVE_TIME NUMBER)
RETURN new_type AS new_type_variable
BEGIN
  SELECT SEAT_NO 
  INTO new_type_variable.RESERVED_SEAT_NO
  FROM SEAT
  WHERE 
      RESERVED IS NULL 
      AND BOOKED IS NULL 
      AND ROWNUM = 1
      OR BOOKED IS NULL 
      AND (RESERVE_TIME - 5000) <= BOOKING_TIME
      AND ROWNUM = 1;

  IF(RESERVED_SEAT_NO != 'NULL') THEN
    select RESERVE_SEAT(P_NO,ID,RESERVE_TIME,RESERVEd_SEAT_NO) into new_type_variable.res from dual;
  END IF;
  RETURN new_type_variable;
END GET_FREE_SEAT;