MyBatis：条件构造器QueryWrapper方法详解

MyBatis：条件构造器QueryWrapper方法详解 

目录

• QueryWrapper
• 1. eq、ne
• 2. gt、ge、lt、le
• 3. between、notBetween
• 4. like、notLike、likeLeft、likeRight
• 5. isNull、isNotNull
• 6. in、notIn
• 7. or、and
• 8. orderByAsc、orderByDesc
• 9. inSql、notInSql (不常用)
• 10. exists、notExists (不常用)

 

正文

QueryWrapper

说明:
      继承自 AbstractWrapper ,自身的内部属性 entity 也用于生成 where 条件
及 LambdaQueryWrapper, 可以通过 new QueryWrapper().lambda() 方法获取.

测试用表：

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1. eq、ne

说明：

eq：等于，ne：不等于

测试：

@Test
public void contextLoads(){
        QueryWrapper<Employee> wrapper = new QueryWrapper<>();
        //eq() 等于
        wrapper.eq("last_name", "皮皮虾");
        Employee one = employeeService.getOne(wrapper);
        System.out.println(one);
}

@Test
public void contextLoads(){
        QueryWrapper<Employee> wrapper = new QueryWrapper<>();
        //ne() 不等于
        wrapper.ne("gender", 0);
        List<Employee> list = employeeService.list(wrapper);
        System.out.println(list);
}

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2. gt、ge、lt、le

说明：

gt：大于，ge：大于等于，lt：小于，le：小于等于

测试：

@Test
public void contextLoads(){
        QueryWrapper<Employee> gtWrapper = new QueryWrapper<>();
        //gt() 大于
        gtWrapper.gt("age", 27);
        List<Employee> gtList = employeeService.list(gtWrapper);
        System.out.println(gtList);

        //**********************

        QueryWrapper<Employee> geWrapper = new QueryWrapper<>();
        //ge() 大于等于
        geWrapper.ge("age", 26);
        List<Employee> geList = employeeService.list(geWrapper);
        System.out.println(geList);
}

@Test
public void contextLoads(){
        QueryWrapper<Employee> ltWrapper = new QueryWrapper<>();
        //lt() 小于
        ltWrapper.lt("age", 12);
        List<Employee> ltList = employeeService.list(ltWrapper);
        System.out.println(ltList);

        //**********************

        QueryWrapper<Employee> geWrapper = new QueryWrapper<>();
        //le() 小于等于
        leWrapper.le("age", 12);
        List<Employee> leList = employeeService.list(leWrapper);
        System.out.println(leList);
}

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3. between、notBetween

说明：

between：在值1和值2之间，notBetween：不在值1和值2之间

测试：

@Test
public void contextLoads(){
        QueryWrapper<Employee> betweenWrapper = new QueryWrapper<>();
        //between() 区间的值
        betweenWrapper.between("age", 10, 20);
        List<Employee> betweenList = employeeService.list(betweenWrapper);
        System.out.println(betweenList );

        //**********************

        QueryWrapper<Employee> notBetweenWrapper = new QueryWrapper<>();
        //notBetween() 不在区间的值
        notBetweenWrapper.notBetween("age", 10, 21);
        List<Employee> notBetweenList = employeeService.list(notBetweenWrapper );
        System.out.println(notBetweenList );
}

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4. like、notLike、likeLeft、likeRight

说明：

like：’%值%’，notLike：’%值%’，likeLeft：’%值’，likeRight：'值%'

测试：

@Test
public void contextLoads(){
        QueryWrapper<Employee> likeWrapper = new QueryWrapper<>();
        //like() 模糊查询匹配值
        likeWrapper.like("last_name", "s");
        List<Employee> likeList = employeeService.list(likeWrapper);
        System.out.println(likeList );

        //**********************

        QueryWrapper<Employee> notLikeWrapper = new QueryWrapper<>();
        //notLike() 模糊查询不匹配值
        notLikeWrapper.notLike("last_name", "s");
        List<Employee> notLikeList = employeeService.list(notLikeWrapper);
        System.out.println(notLikeList);
}

@Test
public void contextLoads(){
        QueryWrapper<Employee> likeLeftWrapper = new QueryWrapper<>();
        //likeLeft() 模糊查询匹配最后一位值
        likeLeftWrapper.likeLeft("last_name", "s");
        List<Employee> likeLeftList = employeeService.list(likeLeftWrapper);
        System.out.println(likeLeftList );

        //**********************

        QueryWrapper<Employee> likeRightWrapper = new QueryWrapper<>();
        //likeRight() 模糊查询匹配第一位值
        likeRightWrapper.likeRight("last_name", "s");
        List<Employee> likeRightList = employeeService.list(likeRightWrapper );
        System.out.println(likeRightList );
}

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5. isNull、isNotNull

说明：

isNull：字段 IS NULL，isNotNull：字段 IS NOT NULL

测试：

@Test
public void contextLoads(){
        QueryWrapper<Employee> isNullWrapper = new QueryWrapper<>();
        //isNull() 为空
        isNullWrapper.isNull("email");
        List<Employee> isNullList = employeeService.list(isNullWrapper);
        System.out.println(isNullList );

        //**********************

        QueryWrapper<Employee> isNotNullWrapper = new QueryWrapper<>();
        //isNotNull() 不为空
        isNotNullWrapper.isNotNull("last_name", "s");
        List<Employee> isNotNullList = employeeService.list(isNotNullWrapper );
        System.out.println(isNotNullList );
}

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6. in、notIn

说明：

in：字段 IN (v0, v1, …)，notIn：字段 NOT IN (value.get(0), value.get(1), …)

测试：

@Test
public void contextLoads(){
        QueryWrapper<Employee> inWrapper = new QueryWrapper<>();
        //in() 符合多个条件的值
        inWrapper.in("age", 8, 16, 26);
        List<Employee> inList = employeeService.list(inWrapper);
        System.out.println(inList );

        //**********************

        QueryWrapper<Employee> notInWrapper= new QueryWrapper<>();
        //notIn() 不符合多个条件的值
        notInWrapper.notIn("age", 8, 16, 26);
        List<Employee> notInList = employeeService.list(notInWrapper);
        System.out.println(notInList );
}

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7. or、and

说明：

or：或者 ，and：和

注意事项:
主动调用or表示紧接着下一个方法不是用and连接!(不调用or则默认为使用and连接)

测试：

@Test
public void contextLoads(){
        QueryWrapper<Employee> orWrapper = new QueryWrapper<>();
        //or() 查询age大于20 或者 gender等于1 的数据
        orWrapper.gt("age", 20).or().eq("gender", 1);
        List<Employee> orList = employeeService.list(orWrapper);
        System.out.println(orList );
}

@Test
public void contextLoads(){
        QueryWrapper<Employee> andWrapper = new QueryWrapper<>();
        //and() 查询last_name等于皮皮虾b 和 gender等于1 的数据 (不使用and() 默认就是and())
        andWrapper.eq("last_name", "皮皮虾b").eq("gender", 1);
        List<Employee> andList = employeeService.list(andWrapper );
        System.out.println(andList);
}

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8. orderByAsc、orderByDesc

说明：

orderByAsc：升序：ORDER BY 字段, … ASC，orderByDesc：降序：ORDER BY 字段, … DESC

测试：

@Test
public void contextLoads(){
        QueryWrapper<Employee> Wrapper = new QueryWrapper<>();
        //orderByAsc() 升序排序
        Wrapper.orderByAsc("id");
        List<Employee> list = employeeService.list(Wrapper);
        for(Employee e : list) {
            System.out.println(e);
        }
}

@Test
public void contextLoads(){
        QueryWrapper<Employee> Wrapper = new QueryWrapper<>();
        //orderByDesc() 降序排序
        Wrapper.orderByDesc("id");
        List<Employee> list = employeeService.list(Wrapper);
        for(Employee e : list) {
            System.out.println(e);
        }
}

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9. inSql、notInSql (不常用)

说明：

inSql：字段 IN ( sql语句 )，notInSql：字段 NOT IN ( sql语句 )

测试：

@Test
public void contextLoads(){
        QueryWrapper<Employee> inSqlWrapper = new QueryWrapper<>();
        //inSql() 符合sql语句的值
        inSqlWrapper .inSql("select id from employee where id < 10");
        List<Employee> inSqlList = employeeService.list(inSqlWrapper );
        System.out.println(inSqlList );

        //**********************

        QueryWrapper<Employee> notInSqlWrapper= new QueryWrapper<>();
        //notInSql() 不符合sql语句的值
        notInSqlWrapper.notInSql("select id from employee where id < 10");
        List<Employee> notInSqlList = employeeService.list(notInSqlWrapper);
        System.out.println(notInSqlList );
}

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10. exists、notExists (不常用)

说明：

exists：拼接 EXISTS ( sql语句 )，notExists：拼接 NOT EXISTS ( sql语句 )

测试：

@Test
public void contextLoads(){
        QueryWrapper<Employee> existsWrapper = new QueryWrapper<>();
        //exists() 查询符合sql语句的值
        existsWrapper.exists("select last_name,gender from employee where id = 1");
        List<Employee> existsList = employeeService.list(existsWrapper);
        System.out.println(existsList );

        //**********************

        QueryWrapper<Employee> notExistsWrapper = new QueryWrapper<>();
        //notExists() 查询不符合sql语句的值
        notExistsWrapper.notExists("select last_name,gender from employee where id = 1");
        List<Employee> notExistsList = employeeService.list(notExistsWrapper);
        System.out.println(notExistsList );

}