原文連結：https://mp.weixin.qq.com/s/9WOmclZjELTNdmdoG6H4oA

哈喽，大家好，我是指北君。

之前有一篇文章，我們介紹過通過 Mybatis Plus 進行增删改查。如下這段代碼：

/**
 * 根據id修改
 * UPDATE user SET user_name=?, user_age=? WHERE (id = ?)
 */
@Test
public void testudpateById(){
    User user = new User();
    user.setUserAge("25");
    user.setUserName("test update");
    UpdateWrapper updateWrapper = new UpdateWrapper();
    updateWrapper.eq("id","3");
    int num = userMapper.update(user, updateWrapper);
    System.out.println("修改的記錄數為："+num);
}
     
/**
 * 查詢指定記錄
 * SELECT id,user_name,user_age FROM user WHERE (user_name = ?)
 */
@Test
public void testSelectWrapper(){
    QueryWrapper wrapper = new QueryWrapper();
    wrapper.eq("user_name","IT可樂");
    List<User> users = userMapper.selectList(wrapper);
    users.forEach(x-> System.out.println(x.getId()+"-"+x.getUserName()+"-"+x.getUserAge()));
}

上面兩個方法分别是根據id修改表記錄，和根據user_name查詢記錄。構造的條件使用了 UpdateWrapper 和 QueryWrapper ，那麼這是什麼呢？其實 mybatis plus 通過條件構造器可以組成複雜的SQL語句。本篇部落格我們将詳細介紹。

1、Wrapper

Mybatis Plus 提供的幾種條件構造器，關系如下：

我們主要通過 QueryWrapper 和 UpdateWrapper 進行條件構造，這兩個和 LambdaQueryWrapper、LambdaUpdateWrapper 差不多是等價的，隻不過後者采用了 JDK1.8 提供的lambda 文法，使用起來更簡潔。

2、文法詳情總結

關于條件構造器的各個用法介紹，可以參考官網：https://mp.baomidou.com/guide/wrapper.html#abstractwrapper

這裡我們做一下總結：

方法名說明用法執行個體等價SQL官網位址https://mp.baomidou.com/guide/wrapper.html#abstractwrapper----::----:allEq(Map<R, V> params)全部等于map.put("id","3");map.put("user_name","IT可樂");allEq(map)user_name = "IT可樂" AND id = 3eq(R column, Object val)等于 =eq("id","3")id = 3ne(R column, Object val)不等于 <>ne("id", "3")id <> 3gt(R column, Object val)大于 >gt("user_age","18")user_age > 18ge(R column, Object val)大于等于 >=ge("user_age","18")user_age >= 18lt(R column, Object val)小于 <lt("user_age","18")user_age < 18le(R column, Object val)小于等于 <=le("user_age","18")user_age <= 18between(R column, Object val1, Object val2)BETWEEN 值1 AND 值2between("user_age","18","25")user_age BETWEEN 18 AND 25notBetween(R column, Object val1, Object val2)NOT BETWEEN 值1 AND 值2notBetween("user_age","18","25")user_age NOT BETWEEN 18 AND 25like(R column, Object val)LIKE '%值%'like("user_name","可樂")like ‘%可樂%’notLike(R column, Object val)NOT LIKE '%值%'notLike("user_name","可樂")not like ‘%可樂%’likeLeft(R column, Object val)LIKE '%值'likeLeft("user_name","可樂")like ‘%可樂’likeRight(R column, Object val)LIKE '值%'likeRight("user_name","可樂")like ‘可樂%’isNull(R column)字段 IS NULLisNull("user_name")user_name IS NULLisNotNull(R column)字段 IS NOT NULLisNotNull("user_name")user_name IS NOT NULLin(R column, Collection<?> value)字段 IN (value.get(0), value.get(1), ...)in("user_age",{1,2,3})user_age IN (?,?,?)notIn(R column, Collection<?> value)字段 NOT IN (value.get(0), value.get(1), ...)notIn("user_age",{1,2,3})user_age NOT IN (?,?,?)inSql(R column, String inValue)字段 IN ( sql語句 )inSql("id","select id from user")id IN (select id from user)notInSql(R column, String inValue)字段 NOT IN ( sql語句 )notInSql("id","select id from user where id > 2")id NOT IN (select id from user where id > 2groupBy(R... columns)分組：GROUP BY 字段, ...groupBy("id","user_age")GROUP BY id,user_ageorderByAsc(R... columns)排序：ORDER BY 字段, ... ASCorderByAsc("id","user_age")ORDER BY id ASC,user_age ASCorderByDesc(R... columns)排序：ORDER BY 字段, ... DESCorderByDesc("id","user_age")ORDER BY id DESC,user_age DESCorderBy(boolean condition, boolean isAsc, R... columns)ORDER BY 字段, ...orderBy(true,true,"id","user_age")ORDER BY id ASC,user_age ASChaving(String sqlHaving, Object... params)HAVING ( sql語句 )having("sum(user_age)>{0}","25")HAVING sum(user_age)>25or()拼接 OReq("id",1).or().eq("user_age",25)id = 1 OR user_age = 25and(Consumerconsumer)AND 嵌套and(i->i.eq("id",1).ne("user_age",18))id = 1 AND user_age <> 25nested(Consumerconsumer)正常嵌套不帶 AND 或者 ORnested(i->i.eq("id",1).ne("user_age",18))id = 1 AND user_age <> 25apply(String applySql, Object... params)拼接 sql(不會有SQL注入風險)apply("user_age>{0}","25 or 1=1")user_age >'25 or 1=1'last(String lastSql)拼接到 sql 的最後,多次調用以最後一次為準(有sql注入的風險)last("limit 1")limit 1exists(String existsSql)拼接 EXISTS ( sql語句 )exists("select id from user where user_age = 1")EXISTS (select id from user where user_age = 1)notExists(String notExistsSql)拼接 NOT EXISTS ( sql語句 )notExists("select id from user where user_age = 1")NOT EXISTS (select id from user where user_age = 1)

3、文法詳情示範

對于上表出現的每個文法，這裡通過代碼展示出來。

更多可以參考位址：https://github.com/YSOcean/mybatisplusstudy.git

package com.ys.mybatisplusstudy;
 
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.ys.mybatisplusstudy.entry.User;
import com.ys.mybatisplusstudy.mapper.UserMapper;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
 
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
 
@SpringBootTest
public class WrapperTest {
    @Autowired
    private UserMapper userMapper;
 
 
    /**
     * 新增一條記錄
     */
    @Test
    public void testInsert(){
        User user = new User();
        user.setId(4L);
        user.setUserName("test insert");
        user.setUserAge("1");
        int insert = userMapper.insert(user);
        System.out.println("影響記錄數："+insert);
    }
 
    /**
     * allEq 全部等于
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (user_name = ? AND id = ?)
     */
    @Test
    public void testAllEq(){
        QueryWrapper queryWrapper = new QueryWrapper();
        Map map = new HashMap<>();
        map.put("id","3");
        map.put("user_name","IT可樂");
        queryWrapper.allEq(map);
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
    /**
     * eq 等于
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (id = ?)
     */
    @Test
    public void testEq(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.eq("id","3");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
    /**
     * ne 不等于
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (id <> ?)
     */
    @Test
    public void testNe(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.ne("id","3");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
    /**
     * gt 大于
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (user_age > ?)
     */
    @Test
    public void testGt(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.gt("user_age","18");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
    /**
     * ge 大于等于
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (user_age >= ?)
     */
    @Test
    public void testGe(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.ge("user_age","18");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
    /**
     * lt 小于
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (user_age < ?)
     */
    @Test
    public void testLt(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.lt("user_age","18");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
    /**
     * le 小于等于
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (user_age <= ?)
     */
    @Test
    public void testLe(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.le("user_age","18");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
    /**
     * between 值1和值2之間,兩邊臨界值都包含
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (user_age BETWEEN ? AND ?)
     */
    @Test
    public void testBetween(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.between("user_age","18","25");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
    /**
     * notBetween 不在值1和值2之間，兩邊臨界值都包含
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (user_age NOT BETWEEN ? AND ?)
     */
    @Test
    public void testNoBetween(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.notBetween("user_age","18","25");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
    /**
     * like 模糊查詢，會在參數左右兩邊加上 %
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (user_name LIKE ?)
     */
    @Test
    public void testLike(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.like("user_name","可樂");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
    /**
     * notLike NOT LIKE ‘%parameter%’
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (user_name NOT LIKE ?)
     */
    @Test
    public void testNotLike(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.notLike("user_name","可樂");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
    /**
     * likeLeft LIKE ‘%parameter’
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (user_name LIKE '%parameter')
     */
    @Test
    public void testLikeLeft(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.likeLeft("user_name","可樂");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
    /**
     * likeRight LIKE ‘parameter%’
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (user_name LIKE 'parameter%')
     */
    @Test
    public void testLikeRight(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.likeRight("user_name","可樂");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
    /**
     * isNull 判斷字段為null
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (user_name IS NULL)
     */
    @Test
    public void testIsNull(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.isNull("user_name");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
    /**
     * isNotNull 判斷字段不為null
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (user_name IS NOT NULL)
     */
    @Test
    public void testIsNotNull(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.isNotNull("user_name");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
 
    /**
     * in 範圍定值查詢
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (user_age IN (?,?,?))
     */
    @Test
    public void testIn(){
        QueryWrapper queryWrapper = new QueryWrapper();
        List<Integer> queryList = new ArrayList<>();
        queryList.add(18);
        queryList.add(1);
        queryList.add(25);
        queryWrapper.in("user_age",queryList);
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
    /**
     * notIn
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (user_age IN (?,?,?))
     */
    @Test
    public void testNotIn(){
        QueryWrapper queryWrapper = new QueryWrapper();
        List<Integer> queryList = new ArrayList<>();
        queryList.add(18);
        queryList.add(1);
        queryList.add(25);
        queryWrapper.notIn("user_age",queryList);
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
    /**
     * inSql
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (id IN (select id from user))
     */
    @Test
    public void testInSql(){
        QueryWrapper queryWrapper = new QueryWrapper();
        //查詢所有資料
        queryWrapper.inSql("id","select id from user");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
    /**
     * notInSql
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (id NOT IN (select id from user where id > 2))
     */
    @Test
    public void testNotInSql(){
        QueryWrapper queryWrapper = new QueryWrapper();
        //查詢所有資料
        queryWrapper.notInSql("id","select id from user where id > 2");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
 
    /**
     * groupBy 分組
     * 下面SQL有個問題，在MySQL8.0版本中，是可以執行下面SQL語句的，select user_name并沒有出現在group by 語句中
     * 執行個體SQL：SELECT id,user_name,user_age FROM user GROUP BY id,user_age
     */
    @Test
    public void testGroupBy(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.groupBy("id","user_age");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
 
    /**
     * orderByAsc 升序
     * 執行個體SQL：SELECT id,user_name,user_age FROM user ORDER BY id ASC,user_age ASC
     */
    @Test
    public void testOrderByAsc(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.orderByAsc("id","user_age");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
    /**
     * orderByDesc 降序
     * 執行個體SQL：SELECT id,user_name,user_age FROM user ORDER BY id DESC,user_age DESC
     */
    @Test
    public void testOrderByDesc(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.orderByDesc("id","user_age");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
    /**
     * orderBy 指定順序排序
     * 執行個體SQL：SELECT id,user_name,user_age FROM user ORDER BY id ASC,user_age ASC
     */
    @Test
    public void testOrderBy(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.orderBy(true,true,"id","user_age");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
 
    /**
     * having
     * 執行個體SQL：SELECT id,user_name,user_age FROM user GROUP BY id,user_age HAVING sum(user_age)>?
     */
    @Test
    public void testHaving(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.groupBy("id","user_age");
        queryWrapper.having("sum(user_age)>{0}","25");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
    /**
     * having
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (id = ? OR user_age = ?)
     */
    @Test
    public void testOr(){
        QueryWrapper queryWrapper = new QueryWrapper();
        queryWrapper.eq("id",1);
        queryWrapper.or();
        queryWrapper.eq("user_age",25);
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
    /**
     * and
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE ((id = ? AND user_age <> ?))
     */
    @Test
    public void testAnd(){
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.and(i->i.eq("id",1).ne("user_age",18));
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
 
    /**
     * nested
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE ((id = ? AND user_age <> ?))
     */
    @Test
    public void testNested(){
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.nested(i->i.eq("id",1).ne("user_age",18));
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
    /**
     * apply
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (user_age>?)
     */
    @Test
    public void testApplyd(){
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.apply("user_age>{0}","25 or 1=1");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
    /**
     * last
     * 執行個體SQL：SELECT id,user_name,user_age FROM user limit 1
     */
    @Test
    public void testLast(){
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.last("limit 1 ");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
 
    /**
     * exists
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (EXISTS (select id from user where user_age = 1))
     */
    @Test
    public void testExists(){
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.exists("select id from user where user_age = 1");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
 
 
    /**
     * notExists
     * 執行個體SQL：SELECT id,user_name,user_age FROM user WHERE (EXISTS (select id from user where user_age = 1))
     */
    @Test
    public void testNotExists(){
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.notExists("select id from user where user_age = 1");
        List<User> list = userMapper.selectList(queryWrapper);
        System.out.println(list);
    }
}

4、LambdaQueryWrapper和LambdaUpdateWrapper（推薦）

LambdaQueryWrapper 和 LambdaUpdateWrapper 這是相對于 QueryWrapper 及 UpdateWrapper 的 Lmbda 文法實作方式。

分别通過如下兩種方式擷取：

//兩種方式        
LambdaQueryWrapper queryLambda = new QueryWrapper().lambda();
LambdaQueryWrapper lambdaQueryWrapper = new LambdaQueryWrapper<>();

//兩種方式
LambdaUpdateWrapper updateLambda = new UpdateWrapper().lambda();
LambdaUpdateWrapper lambdaUpdateWrapper = new LambdaUpdateWrapper();

注意：擷取LambdaQueryWrapper 和 LambdaUpdateWrapper 對象時，為了使用lambda文法，要使用泛型。

下面我示範幾個執行個體：

/**
 * LambdaQueryWrapper
 * SQL執行個體：SELECT id,user_name,user_age FROM user WHERE (id = ? AND user_age <> ?)
 */
@Test
public void testLambdaQueryWrapper(){
    LambdaQueryWrapper<User> queryLambda = new LambdaQueryWrapper<>();
    queryLambda.eq(User::getId,"1").ne(User::getUserAge,25);
    List<User> users = userMapper.selectList(queryLambda);
    System.out.println(users);
 
}
 
/**
 * LambdaQueryWrapper
 * SQL執行個體：UPDATE user SET user_name=? WHERE (user_name = ?)
 */
@Test
public void testLambdaUpdateWrapper(){
    User user = new User();
    user.setUserName("LambdaUpdateWrapper");
    LambdaUpdateWrapper<User> userLambdaUpdateWrapper = new LambdaUpdateWrapper<>();
    userLambdaUpdateWrapper.eq(User::getUserName,"IT可樂");
    userMapper.update(user,userLambdaUpdateWrapper);
 
}

5、總結

對于mybatis plus 中的四種條件構造器，我們就到此結束了，大家可以按照我的執行個體敲一遍代碼，基本上就沒啥問題了。

有沒有發現使用 Lambda 文法很爽，文法簡潔，另外有個優點是，使用QueryWrapper或者UpdateWrapper時，對于條件的某個列，我們是寫的字元串配置，比如 QueryWrapper.eq("id",1);這裡的id是資料庫表的列名，很有可能我們會寫錯，但是通過lambda 的方式，LambdaQueryWrapper.eq(User::getId,1)，這樣就不會有寫錯的可能了。是以推薦大家使用Lambda 的方式。

至此，mybatis plus 的正常用法就全部介紹結束了，當然，事情還遠沒有結束，為了讓大家用得更爽，後續将給大家介紹一些高階玩法。

如何通過條件構造器書寫 MybatisPlus 複雜 SQL 語句？

1、Wrapper

2、文法詳情總結

3、文法詳情示範

4、LambdaQueryWrapper和LambdaUpdateWrapper（推薦）

5、總結

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如何通過條件構造器 書寫 MybatisPlus 複雜 SQL 語句？

1、Wrapper

2、文法詳情總結

3、文法詳情示範

4、LambdaQueryWrapper和LambdaUpdateWrapper（推薦）

5、總結

繼續閱讀

如何通過條件構造器書寫 MybatisPlus 複雜 SQL 語句？