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mysql连接查询中and与where的区别浅析

2021-07-01 15:49:57 作者：侣行G_X_N

在使用数据库查询语句时,单表的查询有时候不能满足项目的业务需求,在项目开发过程中,有很多需求都是要涉及到多表的连接查询,这篇文章主要给大家介绍了关于mysql连接查询中and与where区别的相关资料,需要的朋友可以参考下

1. 建表

CREATE TABLE `student`  (
  `id` int(11) NOT NULL,
  `name` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  `age` int(11) NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci ROW_FORMAT = Dynamic;


INSERT INTO `student` VALUES (1, '张三', 12);
INSERT INTO `student` VALUES (2, '李四', 12);
INSERT INTO `student` VALUES (3, '王五', 12);
INSERT INTO `student` VALUES (4, '赵六', 12);
INSERT INTO `student` VALUES (5, '孙七', 12);
INSERT INTO `student` VALUES (6, '王八', 12);

CREATE TABLE `grade`  (
  `id` int(11) NOT NULL,
  `sid` int(11) NULL DEFAULT NULL,
  `grade` int(11) NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci ROW_FORMAT = Dynamic;

INSERT INTO `grade` VALUES (1, 1, 100);
INSERT INTO `grade` VALUES (2, 2, 80);
INSERT INTO `grade` VALUES (3, 3, 99);
INSERT INTO `grade` VALUES (4, 4, 66);