mybatis 查询

List<CustomerService> customerlist = customerService.selectByExample(customerexample);
//如果在customer_service 表有用户的信息，则返回提示
System.out.println("cus:" + (null == customerlist)); // 如果没有查出数据，customerlist 也不是 null，可用 isEmpty() 函数判断，输出： cus:false
if (!customerlist.isEmpty()) {
return new JsonResult(false,"该手机号已经是客服号");
}

mysql 数据类型 java

bigint(20) jdbcType="BIGINT"

enum('0','1') jdbcType="CHAR"

timestamp jdbcType="TIMESTAMP"

text jdbcType="VARCHAR"

char(1) jdbcType="VARCHAR"

smallint(6) jdbcType="BIGINT"

二：建表：

CREATE TABLE `user` (
  `user_id` bigint(10) NOT NULL AUTO_INCREMENT COMMENT '用户Id',
  `name` varchar(40) DEFAULT NULL COMMENT '姓名',
  `password` varchar(30) DEFAULT NULL COMMENT '密码',
  `age` bigint(10) DEFAULT NULL COMMENT '年龄',
  `deleteFlag` enum('0','1') DEFAULT '0' COMMENT '状态',
  PRIMARY KEY (`user_id`)
) ENGINE=InnoDB AUTO_INCREMENT=44 DEFAULT CHARSET=utf8mb4

创建User对象：

private Long user_id;
private String name;
private String password;
private Long age;
private String deleteFlag;

删除表记录的语句：

User user = new User();
user.setUser_id(4L);

int f = userMapper.deleteUser(user);

<delete id="deleteUser" parameterType="com.dy.entity.User">
delete from user where user_id like CONCAT('%', #{user_id}, '%');
</delete>

如果表中 user_id 有 4 这个数字的有5条记录。删除语句如下：

2018-08-15 18:13:31 [ main:399 ] - [ DEBUG ] ==> Preparing: delete from user where user_id like CONCAT('%', ?, '%');
2018-08-15 18:13:31 [ main:439 ] - [ DEBUG ] ==> Parameters: 4(Long)
2018-08-15 18:13:31 [ main:499 ] - [ DEBUG ] <== Updates: 5

返回的 f 值是 5 。