使用MySQL with 递归查询菜单树

1、使用了MySQL 的with 关键字 配合 RECURSIVE 递归查出用户的菜单。

2、例子如下

　　RBAC（Role-Based Access Control）即：基于角色的权限控制。通过角色关联用户，角色关联权限的方式间接赋予用户权限。

　　下面设计5个表来完成这个控制。

　　t_menu表、t_role表、t_role_menu表、t_user表、t_user_role表。其中t_role_menu表示每个角色里拥有的菜单，t_user_role表示每个用户拥有多少个角色。

　　

-- ----------------------------
-- Table structure for t_menu
-- ----------------------------
DROP TABLE IF EXISTS `t_menu`;
CREATE TABLE `t_menu`  (
  `id` bigint(0) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL COMMENT '菜单名称',
  `url` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL COMMENT '菜单路径',
  `permission_code` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL COMMENT '菜单权限码',
  `icon` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL COMMENT '图标',
  `parent_id` bigint(0) NULL DEFAULT NULL COMMENT '父级ID',
  `sort_number` int(0) NULL DEFAULT NULL COMMENT '排序',
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Table structure for t_role
-- ----------------------------
DROP TABLE IF EXISTS `t_role`;
CREATE TABLE `t_role`  (
  `id` bigint(0) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  `description` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Table structure for t_role_menu
-- ----------------------------
DROP TABLE IF EXISTS `t_role_menu`;
CREATE TABLE `t_role_menu`  (
  `id` bigint(0) NOT NULL AUTO_INCREMENT,
  `role_id` bigint(0) NULL DEFAULT NULL,
  `menu_id` bigint(0) NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Table structure for t_user
-- ----------------------------
DROP TABLE IF EXISTS `t_user`;
CREATE TABLE `t_user`  (
  `id` bigint(0) NOT NULL AUTO_INCREMENT,
  `username` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  `password` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Table structure for t_user_role
-- ----------------------------
DROP TABLE IF EXISTS `t_user_role`;
CREATE TABLE `t_user_role`  (
  `id` bigint(0) NOT NULL AUTO_INCREMENT,
  `user_id` bigint(0) NULL DEFAULT NULL,
  `role_id` bigint(0) NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci ROW_FORMAT = Dynamic;

　　3、查询某个用户的菜单列表如下

　　　　WITH RECURSIVE r(`id`, `name`, `url`, `permission_code`, `icon`, `parent_id`, `sort_number`) AS (
            SELECT DISTINCT d.* FROM t_user_role a
            LEFT JOIN t_role b ON a.role_id = b.id
            LEFT JOIN t_role_menu c ON b.id = c.role_id
            LEFT JOIN t_menu d ON c.menu_id = d.id
            WHERE a.user_id = {userId}
            UNION DISTINCT
            SELECT m.* FROM t_menu m,r WHERE m.id = r.parent_id
            )
        SELECT * FROM r;