Mybatis-Plus常用的增删改查&坑

添加依赖

   <!--实体类上加上@Data注解就不用写get，set，toString，equals等方法了-->
   <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <optional>true</optional>
   </dependency>
   <!--mybatis-plus依赖-->
   <dependency>
      <groupId>com.baomidou</groupId>
      <artifactId>mybatis-plus-boot-starter</artifactId>
      <version>3.1.0</version>
   </dependency>

Mapper接口要继承自BaseMapper并将实体类作为泛型

public interface UserMapper extends BaseMapper<User> {
}

增 insert

User user = new User();
user.setUserName("向南");
user.setAge(32);
user.setEmail("[email protected]");
user.setManagerId(1088248166370832385L);
int rows = userMapper.insert(user);

删 delete

deleteById

@Test
public void deleteById(){
    int rows = userMapper.deleteById(1152147420519170050L);
    System.out.println("删除的记录数："+rows);
}

deleteByMap

/**
 * DELETE FROM user WHERE name = ? AND age = ? 
 */
@Test
public void deleteByMap(){
    HashMap<String, Object> map = new HashMap<>();
    map.put("age",32);
    map.put("name","朱上林");
    int rows = userMapper.deleteByMap(map);
    System.out.println("删除了："+rows+"条记录");
}

deleteBatchIds

@Test
public void deleteBatchIds(){
    int rows = userMapper.deleteBatchIds(
Arrays.asList(1152134491950309377L,
            1152138510835929090L, 1152139353765216258L));
    System.out.println("受影响的行数："+rows);
}

Lambda删除

@Test
public void deleteByLambdaWrapper(){
    LambdaQueryWrapper<User> lambdaWrapper = new LambdaQueryWrapper<>();
    // DELETE FROM user WHERE age = ? OR age > ? 
    lambdaWrapper.eq(User::getAge,32).or().gt(User::getAge,40);
    int rows = userMapper.delete(lambdaWrapper);
    System.out.println("受影响的行数："+rows);
}

改 update

updateById

@Test
public void updateUser(){
    User user = new User();
    user.setId(1094590409767661571L);
    user.setAge(28);
    user.setEmail("[email protected]");
    int rows = userMapper.updateById(user);
    //UPDATE user SET age=?, email=? WHERE id=? 
    System.out.println("受影响的行数： "+rows);
}

update

@Test
public void updateByWrapper(){
    UpdateWrapper<User> wrapper = new UpdateWrapper<>();
    //where条件构造器
    wrapper.eq("name","朱上林");
    //set改变的数据设置
    User user = new User();
    user.setAge(29);
    user.setEmail("[email protected]");
    int rows = userMapper.update(user, wrapper);
    //UPDATE user SET age=?, email=? WHERE name = ?
    System.out.println("受影响的行数： "+rows);
}

查 select

selectById

@Test
public void selectById(){
    User user = userMapper.selectById(1088248166370832385L);
    //SELECT id,name,age,email,manager_id,create_time FROM user WHERE id=?
    System.out.println(user);
}

selectBatchIds

@Test
public void selectBatchIds(){
    List<Long> idList = Arrays.asList(1087982257332887553L, 1094590409767661571L, 1152134491950309377L);
    List<User> userList = userMapper.selectBatchIds(idList);
    //SELECT id,name,age,email,manager_id,create_time FROM user WHERE id IN ( ? , ? , ? )
    userList.forEach(System.out::println);
}

selectByMap

@Test
public void selectByMap(){
    HashMap<String, Object> map = new HashMap<>();
    map.put("name", "朱上林");
    map.put("age",26);
//注意map中的key是表中的列，不是实体类中的属性
    List<User> userList = userMapper.selectByMap(map);
    //SELECT id,name,age,email,manager_id,create_time FROM user WHERE name = ? AND age = ?
    userList.forEach(System.out::println);
}

条件构造器查询

/**
*查询名字包含"雨"子，并且年龄小于40
*/
@Test
public void selectByWrapper(){
    //创建一个查询条件构造器对象
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    //构造器赋予条件: WHERE name LIKE ? AND age < ?
    wrapper.like("name", "%雨%").lt("age",40);
    //执行条件构造器查询
    List<User> userList = userMapper.selectList(wrapper);
    //遍历输出结果
    userList.forEach(System.out::println);
}

/*
查询名字包含"雨"子，并且年龄大于等于20，小于等于40，并且email不为null
 */
@Test
public void selectByWrapper2(){
    //创建一个查询条件构造器对象
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    //构造器赋予条件:WHERE name LIKE ? AND age BETWEEN ? AND ? AND email IS NOT NULL
    wrapper.like("name", "%雨%")
.between("age",20,40)
.isNotNull("email");
    //执行条件构造器查询
    List<User> userList = userMapper.selectList(wrapper);
    //遍历输出结果
    userList.forEach(System.out::println);
}

/*
查询名字为"王"姓，或者年龄大于等于26，先按照年龄降序排列，年龄相同的按照id升序排列
 */
@Test
public void selectByWrapper3(){
    //创建一个查询条件构造器对象
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    //构造器赋予条件:WHERE name LIKE 王% OR age >= 26 ORDER BY age DESC , id ASC 
   wrapper.likeRight("name","王")
           .or().ge("age",26)
           .orderByDesc("age")
           .orderByAsc("id");
    //执行条件构造器查询
    List<User> userList = userMapper.selectList(wrapper);
    //遍历输出结果
    userList.forEach(System.out::println);
}

/*
查询创建日期为2019-2-14，并且直属上级领导 姓"王"
 */
@Test
public void selectByWrapper4(){
    //创建一个查询条件构造器对象
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    //构造器赋予条件:create_time字段格式化为"年-月-日"后值为2019-02-14，并且，直属上级姓"王"（子查询）
    //WHERE date_format(create_time,'%Y-%m-%d') = ? AND manager_id IN (select id from user where name like '王%') 
   wrapper.apply("date_format(create_time,'%Y-%m-%d') = {0}","2019-02-14")
           .inSql("manager_id","select id from user where name like '王%'");
    //执行条件构造器查询
    List<User> userList = userMapper.selectList(wrapper);
    //遍历输出结果
    userList.forEach(System.out::println);
}

/*
查询名字为"王"姓 且（年龄小于40或邮箱不为空）
 */
@Test
public void selectByWrapper5(){
    //创建一个查询条件构造器对象
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    //构造器赋予条件:WHERE name LIKE ? AND ( age < ? OR email IS NOT NULL )
//wrap->wrap表示将wrapper传一个到后面，前面是一个整体，后面是一个整体，两个整体再and
    wrapper.likeRight("name","王").and(wrap->wrap.lt("age",40).or().isNotNull("email"));
    //执行条件构造器查询
    List<User> userList = userMapper.selectList(wrapper);
    //遍历输出结果
    userList.forEach(System.out::println);
}

/*
查询年龄大于40 或者（年龄大于20并且邮箱不为空）
 */
@Test
public void selectByWrapper6(){
    //创建一个查询条件构造器对象
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    //构造器赋予条件:WHERE age < ? OR ( age >= ? AND email IS NOT NULL ) 
    wrapper.lt("age",40).or(wrap->wrap.ge("age",20).isNotNull("email"));
    //执行条件构造器查询
    List<User> userList = userMapper.selectList(wrapper);
    //遍历输出结果
    userList.forEach(System.out::println);
}

/*
查询(年龄小于40或者邮箱不为空) 并且 名字为"王"姓
 */
@Test
public void selectByWrapper7(){
    //创建一个查询条件构造器对象
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    //构造器赋予条件:WHERE ( age < ? OR email IS NOT NULL ) AND name LIKE ? 
    wrapper.nested(wq->wq.lt("age",40).or().isNotNull("email")).likeRight("name","王");
    //执行条件构造器查询
    List<User> userList = userMapper.selectList(wrapper);
    //遍历输出结果
    userList.forEach(System.out::println);
}

/*
查询年龄是30，31，32，33
age in (30,31,32,33)
 */
@Test
public void selectByWrapper8(){
    //创建一个查询条件构造器对象
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    //构造器赋予条件:WHERE age IN (?,?,?,?) 
    wrapper.in("age",Arrays.asList(30,31,32,33));
    //执行条件构造器查询
    List<User> userList = userMapper.selectList(wrapper);
    //遍历输出结果
    userList.forEach(System.out::println);
}

常用构造器

常用条件构造器：
等于 =
例: eq("name", "老王")--->name = '老王'
不等于 <>
例: ne("name", "老王")--->name <> '老王'
大于 >
例: gt("age", 18)--->age > 18
大于等于 >=
例: ge("age", 18)--->age >= 18
小于 <
例: lt("age", 18)--->age < 18
小于等于 <=
例: le("age", 18)--->age <= 18
BETWEEN 值1 AND 值2
例: between("age", 18, 30)
--->age between 18 and 30
NOT BETWEEN 值1 AND 值2
例: notBetween("age", 18, 30)
--->age not between 18 and 30
LIKE '%值%'
例: like("name", "王")
--->name like '%王%'
NOT LIKE '%值%'
例: notLike("name", "王")
--->name not like '%王%'
LIKE '%值'
例: likeLeft("name", "王")
--->name like '%王'
LIKE '值%'
例: likeRight("name", "王")
--->name like '王%'
字段 IS NULL
例: isNull("name")
--->name is null
字段 IS NOT NULL
例: isNotNull("name")
--->name is not null
字段 IN 
例: in("age",{1,2,3})
--->age in (1,2,3)
字段NOTIN
例: notIn("age",{1,2,3})
--->age not in (1,2,3)
字段 IN ( sql语句 )
例: inSql("id", "select id from table where id < 3")
--->id in (select id from table where id < 3)
字段 NOT IN ( sql语句 )
例: notInSql("id", "select id from table where id < 3")
--->age not in (select id from table where id < 3)
分组：GROUP BY 字段, ...
例: groupBy("id", "name")
--->group by id,name
排序：ORDER BY 字段, ... ASC
例: orderByAsc("id", "name")
--->order by id ASC,name ASC
排序：ORDER BY 字段, ... DESC
例: orderByDesc("id", "name")
--->order by id DESC,name DESC
HAVING ( sql语句 )
例: having("sum(age) > 10")
--->having sum(age) > 10
例: having("sum(age) > {0}", 11)
--->having sum(age) > 11
OR 拼接
例: eq("id",1).or().eq("name","老王")
--->id = 1 or name = '老王'
OR 嵌套
例: or(i -> i.eq("name", "李白").ne("status", "活着"))
--->or (name = '李白' and status <> '活着')
AND 嵌套
例: and(i -> i.eq("name", "李白").ne("status", "活着"))
--->and (name = '李白' and status <> '活着')
apply拼接sql
例: apply("date_format(dateColumn,'%Y-%m-%d') = {0}", "2008-08-08")
--->date_format(dateColumn,'%Y-%m-%d') = '2008-08-08'")

查询部分字段

/**
*查询指定的字段
*/
@Test
public void selectByWrapperSuper(){
    //创建一个查询条件构造器对象
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    //构造器赋予条件: SELECT id,name FROM user WHERE name LIKE ? AND age < ? 
    wrapper.select("id","name").like("name", "%雨%").lt("age",40);
    //执行条件构造器查询
    List<User> userList = userMapper.selectList(wrapper);
    //遍历输出结果
    userList.forEach(System.out::println);
}

/**
 * 查询除了name和age的所有有字段，名字中包含"雨"，且年龄小于40
 */
@Test
public void selectByWrapperSuper2(){
    //创建一个查询条件构造器对象
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    //构造器赋予条件: SELECT id,name FROM user WHERE name LIKE ? AND age < ?
    wrapper.like("name", "%雨%").lt("age",40)
.select(User.class,info->!info.getColumn().equals("name")
                    &&!info.getColumn().equals("age"));
    //执行条件构造器查询
    List<User> userList = userMapper.selectList(wrapper);
    //遍历输出结果
    userList.forEach(System.out::println);
}

条件查询

@Test
public void testContdition(){
    String name = "王";
    String email = "";
    //WHERE name LIKE ? ，因为email为空，所以不加入到条件构造器中
    condition(name, email);
}

private void condition(String name, String email){
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    //当传过来的参数name，email不为空字符串时，才加入到查询构造器中
    wrapper.like(StringUtils.isNotEmpty(name),"name",name)
            .like(StringUtils.isNotEmpty(email),"email",email);
    List<User> userList = userMapper.selectList(wrapper);
    userList.forEach(System.out::println);
}

创建条件构造器时，传入实体对象

 /*
创建条件构造器时，传入实体对象，就可以代替构造条件wrapper...
  */
 @Test
 public void selectByWrapperEntity(){
     //创建实体对象
     User user = new User();
     user.setAge(26);//相当于WHERE age=26
     //创建一个查询条件构造器对象
     QueryWrapper<User> wrapper = new QueryWrapper<>(user);
     //使用实体对象，就不用构造条件了
     List<User> userList = userMapper.selectList(wrapper);
     //遍历输出结果
     userList.forEach(System.out::println);
 }

allEq

@Test
public void selectByWrapperAllEq(){

    //创建一个查询条件构造器对象
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    //创建一个参数map对象
    HashMap<String, Object> params = new HashMap<>();
    params.put("name", "王天风");
    params.put("age", null);
    wrapper.allEq(params);
    //WHERE name = ? AND age IS NULL
    List<User> userList = userMapper.selectList(wrapper);
    
    userList.forEach(System.out::println);
}

selectMaps

@Test
public void selectByWrapperMaps(){

    //创建一个查询条件构造器对象
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    wrapper.select("id","name").like("name", "雨").lt("age", 40);
    List<Map<String, Object>> maps = userMapper.selectMaps(wrapper);
    /**
     * 这样查询结果只有我们想要的字段和对应的值，没有很多没用的字段和对应的值为null
     * {name=张雨琪, id=1094590409767661570}
     * {name=刘红雨, id=1094592041087729666}
     */
    maps.forEach(System.out::println);
}
/**
 * 按照直属上级分组，查询每组最大年龄，平均年龄，最小年龄，并且只取年龄总和小于500的组
 * select avg(age) avg_age,max(age) max_age,min(age) min_age
 * from user
 * group by manager_id
 * having sum(age)<500
 */
@Test
public void selectByWrapperMaps02(){

    //创建一个查询条件构造器对象
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    wrapper.select("avg(age) avg_age", "max(age) max_age", "min(age) min_age")
            .groupBy("manager_id")
            .having("sum(age)<{0}", 500);
    List<Map<String, Object>> maps = userMapper.selectMaps(wrapper);
    /**
     * {max_age=40, avg_age=40.0000, min_age=40}
     * {max_age=25, avg_age=25.0000, min_age=25}
     * {max_age=33, avg_age=29.6250, min_age=26}
     */
    maps.forEach(System.out::println);
}

selectCount

/**
 * 查询名字中有"雨"子的记录数量
* 注意查询记录数量，不能查询具体的列名
 */
@Test
public void selectCount(){
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    wrapper.like("name","雨");
    Integer count = userMapper.selectCount(wrapper);
    System.out.println(count);
}

Lambda条件构造器

好处：可以放置列名写错，写错编译就不通过

VehicleBO one = vehicleService.getOne(Wrappers.<VehicleBO>lambdaQuery().eq(VehicleBO::getVin, reqVo.getVin()));

/**
 * Lambda条件构造器
 * 查询王姓，年龄小于40
 */
@Test
public void selectLambdaWrapper(){
    // 创建Lambda条件构造器
    LambdaQueryWrapper<User> lambdaWrapper = new LambdaQueryWrapper<>();
    //设置Lambda条件：WHERE name LIKE ? AND age < ? 
    lambdaWrapper.like(User::getName,"雨").lt(User::getAge, 40);

    List<User> userList = userMapper.selectList(lambdaWrapper);
    userList.forEach(System.out::println);
}

/**
 * Lambda条件构造器
 * name like '王%' and (age<40or email is not null)
 */
@Test
public void selectLambdaWrapper2(){
    // 创建Lambda条件构造器
    LambdaQueryWrapper<User> lambdaWrapper = new LambdaQueryWrapper<>();
    //设置Lambda条件：WHERE name LIKE ? AND ( age < ? OR email IS NOT NULL ) 
    lambdaWrapper.likeRight(User::getName,"王")
            .and(lwq->lwq.lt(User::getAge,40)//and(lwq->lwq)嵌套
.or().isNotNull(User::getEmail));//or()拼接

    List<User> userList = userMapper.selectList(lambdaWrapper);
    userList.forEach(System.out::println);
}

分页查询

配置分页插件类

分页查询selectPage

 /*
 分页查询：年龄大于26岁
*/
 @Test
 public void selectPage(){
     //创建一个查询条件构造器对象
     QueryWrapper<User> wrapper = new QueryWrapper<>();
     wrapper.gt("age",26);
     //创建一个Page对象：从第一页开始查询，每页5条数据
     Page<User> page = new Page<>(1, 5);
/**
 *  Page<User> page = new Page<>(1, 5,false);
*  这样表示不查询总记录数
 */
     //selectPage返回一个Ipage对象
     IPage<User> iPage = userMapper.selectPage(page, wrapper);
     //Ipage对象中有总页数，总记录条数，所有记录的get方法
     System.out.println("总页数"+iPage.getPages());
     System.out.println("总记录条数"+iPage.getTotal());
     List<User> userList = iPage.getRecords();
     userList.forEach(System.out::println);
 }

 /*
 分页查询：年龄大于26岁的姓名和年龄
*/
 @Test
 public void selectMapPage(){
     //创建一个查询条件构造器对象
     QueryWrapper<User> wrapper = new QueryWrapper<>();
     wrapper.select("name", "age").gt("age",26);
     //创建一个Page对象：从第一页开始查询，每页5条数据
     Page<User> page = new Page<>(1, 5);
     //selectPage返回一个Ipage对象
     IPage<Map<String, Object>> iPage = userMapper.selectMapsPage(page, wrapper);
     //Ipage对象中有总页数，总记录条数，所有记录的get方法
     System.out.println("总页数"+iPage.getPages());
     System.out.println("总记录条数"+iPage.getTotal());
     List<Map<String, Object>> userList = iPage.getRecords();
     userList.forEach(System.out::println);
 }

坑

Cause: java.sql.SQLIntegrityConstraintViolationException: ORA-01400: 无法将 NULL 插入 ("ZHXY_RSW_LOCAL"."T_EXAM_SUBJECT"."ID")

使用mybatis-plus插入时，明明设置了id的值，还报这个错

在id字段上，添加 @TableId(type = IdType.INPUT)