mysql多對多查詢 原生寫法

准備工作，1.創建表

CREATE TABLE IF NOT EXISTS `users` (
    `id` INTEGER NOT NULL AUTO_INCREMENT,
    `name` VARCHAR(255) NOT NULL,
    PRIMARY KEY (`id`)
) ENGINE = InnoDB CHARSET = utf8mb4;

CREATE TABLE IF NOT EXISTS `applications` (
    `id` INTEGER NOT NULL AUTO_INCREMENT,
    `systemName` VARCHAR(255) NOT NULL,
    PRIMARY KEY (`id`)
) ENGINE = InnoDB CHARSET = utf8mb4;

CREATE TABLE IF NOT EXISTS `user_application` (
    `id` INTEGER NOT NULL AUTO_INCREMENT,
    `applicationId` INTEGER NOT NULL,
    `userId` INTEGER NOT NULL,
    `type` TINYINT,
    UNIQUE `user_application_applicationId_userId_unique` (`applicationId`, `userId`),
    PRIMARY KEY (`id`)
) ENGINE = InnoDB CHARSET = utf8mb4;

2.創建數據

INSERT INTO `users` (`name`) VALUES ('張三'),('李四'),('老王'),('小明'),('濤哥');
INSERT INTO `applications` (`systemName`) VALUES ('mac'),('windows'),('linux'),('android'),('qilin');
INSERT INTO `user_application` (`applicationId`,`userId`,`type`) VALUES (1,1,1),(2,1,2),(3,1,2),(2,2,1),(2,2,4);

3.使用多對多 關聯查詢... 一個用戶可以有多個應用，一個應用對應多個用戶

查詢“張三”下應用：

SELECT users.id, users.name, user_application.type, applications.systemName
FROM users
    LEFT JOIN (user_application `user_application`
        INNER JOIN applications `applications` ON user_application.applicationId = applications.id) ON users.id = user_application.userId
WHERE users.name = '張三'

查詢“windows”下用戶：

SELECT applications.systemName, users.name, user_application.type
FROM applications
    LEFT JOIN (user_application `user_application`
        INNER JOIN users `users` ON user_application.userId = users.id) ON applications.id = user_application.applicationId
WHERE applications.systemName = 'windows'