检查mySQL中的多个表

Question

题:

我是mySQL的新手,我甚至不知道从哪里开始.我想知道如何编写一个简单的函数,它根据分布在许多表中的值返回true或false.

细节:

这是我的表格的相关部分(所有引擎都是innodb).在阅读时,您将看到数据库只是为这些用户/组存储用户,组,文件以及这些文件的权限.

USER表:

CREATE TABLE IF NOT EXISTS USER
(
   ID                 INT NOT NULL auto_increment,

   PRIMARY KEY(ID)
)

GROUP表:

CREATE TABLE IF NOT EXISTS GROUP
(
   ID           INT NOT NULL AUTO_INCREMENT,

   PRIMARY KEY(ID)
)

GROUP MEMBERSHIP表:

CREATE TABLE IF NOT EXISTS GROUPMEMBERSHIP
(
   ID           INT NOT NULL AUTO_INCREMENT,
   USERID       INT NOT NULL,
   GROUPID      INT NOT NULL,

   UNIQUE ( USERID, GROUPID ),
   PRIMARY KEY(ID),
   FOREIGN KEY (USERID) REFERENCES USER(ID),
   FOREIGN KEY (GROUPID) REFERENCES GROUP(ID)
)

文件表:(R,W,X,用于other)

CREATE TABLE IF NOT EXISTS FILE
(
   ID                 INT NOT NULL AUTO_INCREMENT,
   READ               BOOLEAN DEFAULT FALSE,
   WRITE              BOOLEAN DEFAULT FALSE,
   EXECUTE            BOOLEAN DEFAULT FALSE,

   PRIMARY KEY(ID)
)

文件用户权限表:

CREATE TABLE IF NOT EXISTS FILEUSERPERMISSIONS
(
   ID           INT NOT NULL AUTO_INCREMENT,
   FILEID       INT NOT NULL,
   USERID       INT NOT NULL,
   READ         BOOLEAN DEFAULT FALSE,
   WRITE        BOOLEAN DEFAULT FALSE,
   EXECUTE      BOOLEAN DEFAULT FALSE,

   UNIQUE (FILEID, USERID),
   PRIMARY KEY(ID),
   FOREIGN KEY (FILEID) REFERENCES FILE(ID),
   FOREIGN KEY (USERID) REFERENCES USER(ID)
)

文件组许可表:

CREATE TABLE IF NOT EXISTS FILEGROUPPERMISSIONS
(
   ID           INT NOT NULL AUTO_INCREMENT,
   FILEID       INT NOT NULL,
   GROUPID      INT NOT NULL,
   READ         BOOLEAN DEFAULT FALSE,
   WRITE        BOOLEAN DEFAULT FALSE,
   EXECUTE      BOOLEAN DEFAULT FALSE,

   UNIQUE (FILEID, GROUPID),
   PRIMARY KEY(ID),
   FOREIGN KEY (FILEID) REFERENCES FILE(ID),
   FOREIGN KEY (GROUPID) REFERENCES GROUP(ID)
)

hasPermission函数:

DELIMITER $$
DROP FUNCTION IF EXISTS hasPermission$$
CREATE FUNCTION hasPermission(fileID INT, userID INT)
RETURNS BOOLEAN
BEGIN
   ???
END$$
DELIMITER ;

我将如何进行,或者至少在哪里开始编写hasPermission函数,以便在查询时如此:

SELECT hasPermission( 123, 456)

它执行以下操作:

1. 检查文件123是否可读 other
2. 检查用户456是否具有文件123的读取权限
3. 检查用户456是否在某个组中,该组对文件123具有读取权限

第一个是 很琐碎三者中最琐碎的.第二个让我难过.第三个对我来说是一个概念障碍.除此之外,我显然必须检查用户和/或文件是否存在.

请善待,因为我是MySQL的新手.

先谢谢你

Answer 1

检查文件的权限。我可能会这样做：

SELECT
    (
        CASE WHEN EXISTS
            (
                SELECT
                    NULL
                FROM
                    FILE
                WHERE EXISTS
                    (
                        SELECT
                            NULL
                        FROM
                            USER
                            JOIN GROUPMEMBERSHIP
                                ON GROUPMEMBERSHIP.USERID=USER.ID
                            JOIN FILEUSERPERMISSIONS
                                ON FILEUSERPERMISSIONS.USERID=GROUPMEMBERSHIP.USERID
                            JOIN FILEGROUPPERMISSIONS
                                ON FILEGROUPPERMISSIONS.GROUPID=GROUPMEMBERSHIP.GROUPID
                        WHERE 
                            FILEUSERPERMISSIONS.FILEID=FILE.ID
                            AND FILEGROUPPERMISSIONS.FILEID=FILE.ID
                            AND FILEUSERPERMISSIONS.READ=FILE.READ
                            AND FILEGROUPPERMISSIONS.READ=FILE.READ
                            AND USER.ID=userID
                    )
                WHERE
                    FILE.READ=1
                    AND FILE.ID=fileID
            )
        THEN CAST(1 AS BIT)
        ELSE CAST(0 AS BIT)
        END
    ) AS hasRights

但如果你真的想发挥你的功能的价值。我建议使用表函数并只提供userid. 这样就可以获取该用户有权访问的所有文件。这看起来像这样：

SELECT
    ID
FROM
    FILE
WHERE EXISTS
    (
        SELECT
            NULL
        FROM
            USER
            JOIN GROUPMEMBERSHIP
                ON GROUPMEMBERSHIP.USERID=USER.ID
            JOIN FILEUSERPERMISSIONS
                ON FILEUSERPERMISSIONS.USERID=GROUPMEMBERSHIP.USERID
            JOIN FILEGROUPPERMISSIONS
                ON FILEGROUPPERMISSIONS.GROUPID=GROUPMEMBERSHIP.GROUPID
        WHERE 
            FILEUSERPERMISSIONS.FILEID=FILE.ID
            AND FILEGROUPPERMISSIONS.FILEID=FILE.ID
            AND FILEUSERPERMISSIONS.READ=FILE.READ
            AND FILEGROUPPERMISSIONS.READ=FILE.READ
            AND USER.ID=userID
    )
WHERE
    FILE.READ=1

顺便说一下。这个问题问得很好。这应该是如何提问的示例