一些變量保持爲空 - 存儲過程MySQL

我正在用InnoDB數據庫編寫一個小型瀏覽器遊戲。爲了使發生的事情自動化，當你建造一所新房子時，我寫了下面的程序。它的問題是，除了「cycle_offset」之外，每個聲明的變量在第一個SELECT之後仍爲NULL，因此以下三個選擇無法在不傳遞NULL的情況下執行。一些變量保持爲空 - 存儲過程MySQL

DELIMITER // 
DROP PROCEDURE IF EXISTS create_building // 
CREATE PROCEDURE create_building(IN userID INT, IN buildingID INT) 
BEGIN 
--declare variables 
DECLARE cycle_offset INT; 
DECLARE res_1 INT; 
DECLARE am_1 INT; 
DECLARE res_2 INT; 
DECLARE am_2 INT; 
DECLARE res_3 INT; 
DECLARE am_3 INT; 
DECLARE u_am_1 INT; 
DECLARE u_am_2 INT; 
DECLARE u_am_3 INT; 

--fill the values that belong to the certain type of building 
SELECT cycles * 10, 
     res_1, 
     am_1, 
     res_2, 
     am_2, 
     res_3, 
     am_3 
INTO cycle_offset, 
     res_1, 
     am_1, 
     res_2, 
     am_2, 
     res_3, 
     am_3 
FROM build_cost 
WHERE building = buildingID; 

--select resources from user-fortune that were given in the build-cost 
SELECT amount INTO u_am_1 FROM fortune WHERE resource = res_1; 
SELECT amount INTO u_am_2 FROM fortune WHERE resource = res_2; 
SELECT amount INTO u_am_3 FROM fortune WHERE resource = res_3; 
--for each resource: if the resource is not null and the user has more resources left than needed 
--remove the "price" from the user's fortune 
IF 
    ((res_1 IS NOT NULL) AND 
    (u_am_1 >= am_1)) 
THEN 
    UPDATE fortune 
    SET amount = (u_am_1 - am_1) 
    WHERE resource = res_1 AND 
      user = userID; 
END IF; 

IF 
    ((res_1 IS NOT NULL) AND 
    (u_am_2 >= am_2)) 
THEN 
    UPDATE fortune 
    SET amount = (u_am_2 - am_2) 
    WHERE resource = res_2 AND 
      user = userID; 
END IF; 

IF 
    ((res_1 IS NOT NULL) AND 
    (u_am_3 >= am_3)) 
THEN 
    UPDATE fortune 
    SET amount = (u_am_3 - am_3) 
    WHERE resource = res_3 AND 
      user = userID; 
END IF; 

--add the building into the users town 

INSERT INTO town (user, building, cycle_start, level, in_construction) 
VALUES (userID, 
     buildingID, 
     SEC_TO_TIME(FLOOR((TIME_TO_SEC(CURRENT_TIME)+5)/10) * 10 + cycle_offset), 
     1, 
     1); 

--debugging purposes: 
INSERT INTO debug (a,b,c,d,e,f,g,h,i,j,k,l) VALUES (userID, buildingID, cycle_offset, res_1, am_1, res_2, am_2, res_3, am_3, u_am_1, u_am_2, u_am_3); 
END //

調試表總是向我顯示userID，buildingID和cycle_offset不爲空，剩下的是。你能想到的是，「build_cost」 - 表是空的，但是單獨運行查詢給了我這樣的結果（如預期）：

SELECT cycles * 10, res_1, am_1, res_2, am_2, res_3, am_3 
FROM build_cost 
WHERE building = 1; 

+-------------+-------+------+-------+------+-------+------+ 
| cycles * 10 | res_1 | am_1 | res_2 | am_2 | res_3 | am_3 | 
+-------------+-------+------+-------+------+-------+------+ 
|   0 |  4 | 50 |  5 | 50 | NULL | NULL | 
+-------------+-------+------+-------+------+-------+------+

爲什麼是週期，RES_1，am_1，RES_2的價值觀和am_2沒有存儲在我聲明的變量，如果我運行包含此查詢的過程？

來源

2017-04-09 cscholz

我沒有看到你的代碼的任何地方，你要設置RES_3或am_3一個值。 –

'SELECT週期* 10， RES_1， am_1， RES_2， am_2， RES_3， am_3 INTO cycle_offset， RES_1， am_1， RES_2， am_2， RES_3， am_3 FROM build_cost WHERE building = buildingID;' 它應該發生在這裏，還是這是錯的？ – cscholz

只有在這些列中有值時。 –

我在該MySQL interpretes調試器看到

DECLARE cycle_offset INT; 
DECLARE res_1 INT; 
DECLARE am_1 INT; 
DECLARE res_2 INT; 
DECLARE am_2 INT; 
DECLARE res_3 INT; 
DECLARE am_3 INT; 

SELECT cycles * 10, 
     res_1, 
     am_1, 
     res_2, 
     am_2, 
     res_3, 
     am_3 
INTO cycle_offset, 
     res_1, 
     am_1, 
     res_2, 
     am_2, 
     res_3, 
     am_3 
FROM build_cost 
WHERE building = buildingID;

爲

SELECT cycles * 10, 
     NULL, 
     NULL, 
     NULL, 
     NULL, 
     NULL, 
     NULL 
INTO cycle_offset, 
     res_1, 
     am_1, 
     res_2, 
     am_2, 
     res_3, 
     am_3 
FROM build_cost 
WHERE building = buildingID;

因爲，至少它看起來像這樣的變數，如果他們的表列之間不能區分名稱相等。

感謝您的努力，雖然

來源

2017-04-11 06:39:24 cscholz

一些變量保持爲空 - 存儲過程MySQL

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