如何修复“缺少表的 FROM 子句条目”？答案

【问题标题】：How to fix 'missing FROM-clause entry for table'?如何修复“缺少表的 FROM 子句条目”？
【发布时间】：2019-01-15 21:32:42
【问题描述】：

我有一个查询功能。如果条件为真，我用新值更新一行。

我做一个查询：

SELECT * FROM transfer_flight(41313, '2017-08-15 20:00:00+05');

我得到一个错误：

错误：表“航班”缺少 FROM 子句条目第 1 行：选择 (flights.scheduled_departure zone) line 7 at IF

CREATE OR REPLACE FUNCTION flightFunc(
    flight_identificator INTEGER, 
    new_timestamp timestamp with time zone) 
RETURNS TABLE(
    flight_id INTEGER,
    flight_no CHARACTER(6),
    departure_airport character(3),
    scheduled_departure timestamp with time zone,
    arrival_airport character(3),
    scheduled_arrival timestamp with time zone
)
LANGUAGE plpgsql
AS $$
DECLARE 
    flight_d timestamp with time zone =  scheduled_arrival - 
scheduled_departure;

BEGIN

    IF (flights.scheduled_departure < $2)
    THEN
        UPDATE flights
            scheduled_departure = $2,
            scheduled_arrival = $2 + flight_d
        FROM flights
        WHERE flights.flight_id = $1
        RETURNING 
            flights.flight_id,  
            flights.flight_no,
            flights.departure_airport,
            flights.scheduled_departure,
            flights.arrival_airport,        
            flights.scheduled_arrival;
    END IF;

END;
$$;

结果我应该只需要使用输入 flight_identificator 更新一行

【问题讨论】：

标签： sql postgresql sql-update plpgsql

【解决方案1】：

删除FROM 子句！那就是CROSS JOIN。你需要SET。所以：

UPDATE flights
    SET scheduled_departure = $2,
        scheduled_arrival = $2 + flight_d
    WHERE flights.flight_id = $1
RETURNING 
    flights.flight_id,  
    flights.flight_no,
    flights.departure_airport,
    flights.scheduled_departure,
    flights.arrival_airport,        
    flights.scheduled_arrival;

【讨论】：

我创建了一个函数。但是当我在查询中调用函数时： SELECT * FROM transfer_flight(41313, '2017-08-15 20:00:00+05');我从这个问题的主题中得到错误

【解决方案2】：

在我看来，您应该摆脱 flight_d 变量和 IF 块，并将逻辑移至查询本身，例如：

CREATE OR REPLACE FUNCTION flightFunc(
    flight_identificator INTEGER, 
    new_timestamp timestamp with time zone) 
RETURNS TABLE(
    flight_id INTEGER,
    flight_no CHARACTER(6),
    departure_airport character(3),
    scheduled_departure timestamp with time zone,
    arrival_airport character(3),
    scheduled_arrival timestamp with time zone
)
LANGUAGE plpgsql
AS $$

BEGIN

    UPDATE flights SET
        scheduled_departure = $2,
        scheduled_arrival = $2 + flights.scheduled_arrival - flights.scheduled_departure
    WHERE flights.flight_id = $1 AND flights.scheduled_departure < $2
    RETURNING 
        flights.flight_id,  
        flights.flight_no,
        flights.departure_airport,
        flights.scheduled_departure,
        flights.arrival_airport,        
        flights.scheduled_arrival;

END;
$$;

【讨论】：