使用COUNT的SELECT語句

Question

CREATE TABLE hardware 
(
name  varchar(10), 
ID  serial    PRIMARY KEY NOT NULL 
); 

CREATE TABLE games 
(
name  varchar(100), 
ID  serial     PRIMARY KEY 
); 

CREATE TABLE gameVersion 
(
gameID  integer   REFERENCES games(ID), 
version  integer, 
ID  char(10)  PRIMARY KEY  NOT NULL 
); 

CREATE TABLE versionHardware 
(
hardwareID  integer   REFERENCES hardware(ID), 
versionID  char(10)  REFERENCES gameVersion(ID), 
ID  serial   PRIMARY KEY 
); 

CREATE TABLE cheatCodes 
(
ID  serial   PRIMARY KEY  NOT NULL, 
code  varchar(60), 
gameID  integer   REFERENCES games(ID) 
); 

我如何找到任何可以使用ID爲（5）的硬件進行遊戲的記錄上的cheatCodes數量。

我試圖

SELECT COUNT(*) 
    FROM cheatCodes, games, gameVersion,hardware, versionHardware 
    WHERE cheatCodes.GameId = games.ID 
    AND gameVersion.gameID = games.ID 
    AND versionHardware.versionID = gameVersion.ID 
    AND hardware.ID = 5; 

但它不給我正確的答案。

Answer 1

嘗試：

SELECT COUNT(DISTINCT cheatCodes.GameId) as CheatCodeCount 
FROM cheatCodes, games, gameVersion,hardware, versionHardware 
WHERE cheatCodes.GameId = games.ID 
AND gameVersion.gameID = games.ID 
AND versionHardware.versionID = gameVersion.ID 
AND versionHardware.hardwareID = hardware.id 
AND hardware.ID = 5; 

Answer 2

請嘗試下面的查詢。硬件表的鏈接丟失， 鏈接。

SELECT COUNT(*) 
    FROM cheatCodes, games, gameVersion,hardware, versionHardware 
    WHERE cheatCodes.GameId = games.ID 
    AND gameVersion.gameID = games.ID 
    AND versionHardware.versionID = gameVersion.ID 
    AND hardware.id = versionHardware.hardwareID  
    AND hardware.ID = 5;