PostgreSQL函數無法檢測選擇條件

Question

CREATE OR REPLACE FUNCTION heckANDinsert(
    first VARCHAR(20), surname VARCHAR(20), 
    No VARCHAR(30), nation VARCHAR(30), dob DATE 
) RETURNS SETOF passenger AS $$ 
DECLARE 

name VARCHAR(20); 
Sname VARCHAR(20); 
Pass VARCHAR(30); 
nation VARCHAR(30); 
birthdate DATE; 

BEGIN 

SELECT first, same,passportNo, nationality,dob 
INTO fname,sname, PassportN, nation, birthdate 
FROM passenger 
WHERE 
    firstname = $1 
    AND surname = $2 
    AND passportNo = $3 
    AND nationality = $4 
    AND dob = $5; 

IF NOT FOUND THEN 
    INSERT INTO passenger 
    SELECT MAX(passengerid)+1, $1,$2,$3,$4,$5 
    FROM passenger; 
ELSE 
    RAISE EXCEPTION 'passenger record already exists.'; 
END IF; 

END; 
$$ LANGUAGE plpgsql; 

我叫使用

SELECT passenger_checkANDinsert( 
    'john', 'levis', 'v39949455', 'British', '1990-07-23' 
); 

功能將插入正確的結果到數據庫中，如果我更改名字到另一個功能。但如果我更改姓氏並保持與數據庫數據相同的名字，它將不起作用。我想有東西在SELECT語句中錯在何處的功能狀態，但我找不到任何錯誤的..

Answer 1

create or replace function passenger_checkandinsert(
    _firstname varchar(20), _surname varchar(20), 
    _passportno varchar(30), _nationality varchar(30), _dob date 
) returns setof passenger as $$ 

insert into passenger (
    passengerid, firstname, surname, passportNo, nationality, dob 
) 
select coalesce(max(passengerid)+1, 1), $1, $2, $3, $4, $5 
from passenger 
where not exists ( 
    select 1 
    from passenger 
    where 
     firstname = $1 
     and surname = $2 
     and passportno = $3 
     and nationality = $4 
     and dob = $5 
    ) 
returning * 
; 
$$ language sql; 

• 變量使用列的名稱可以是有問題的。只需預先加下劃線即可。
• 聲明您要插入值的列。
• 簡單的SQL將盡你所需。
• 不要做count來檢查行是否存在，因爲它會讀取整個表。而是使用exists，因爲它會停止在第一個找到的行中讀取。
• 注意合併來處理沒有行的情況。
• returning *將返回插入的行。

Answer 2

CREATE OR REPLACE FUNCTION passenger_checkANDinsert 

(firstname VARCHAR(20),surname VARCHAR(20), 

passportNo VARCHAR(30),nationality VARCHAR(30),dob DATE) 

RETURNS SETOF passenger AS 
$$ 

DECLARE 

_exists boolean;  

BEGIN 

SELECT count(*)>0 INTO _exists FROM passenger  
WHERE firstname = $1 AND surname = $2 AND passportNo = $3 AND nationality = $4 AND dob = $5; 

IF NOT _exists THEN 

    INSERT INTO passenger SELECT MAX(passengerid)+1, $1,$2,$3,$4,$5 FROM passenger; 

    ELSE 

    RAISE EXCEPTION 'passenger record already exists.'; 

    END IF; 

END; 

$$ 

    LANGUAGE plpgsql; 

我認爲你正在做的不好用MAX(passengerid)+1，你爲什麼不使用數據類型bigserial？如果你這樣做只是爲了不失去這個領域的一段時間，你是不正確的。

也許你需要通過向列率添加到您的領域：

CREATE SEQUENCE passengerid_seq; 
ALTER TABLE passenger ALTER COLUMN passengerid SET DEFAULT NEXTVAL('passengerid_seq');