项目中需要实现自定义的查询,但是仍然想用QueryWrapper对象里面的那些查询。
案例一(java代码)
LambdaQueryWrapper queryWrapper = new QueryWrapper()
.select("sex, ifnull(count(id), 0) AS num, CASE WHEN sex = 1 THEN '男' WHEN sex = 0 THEN '女' ELSE '未知' END AS sexStr").lambda();
queryWrapper.eq(xxxDO::getStatus, 0);
queryWrapper.groupBy(xxxDO::getSex);
List
执行SQL
select sex, ifnull(count(id), 0) AS num, CASE WHEN sex = 1 THEN '男' WHEN sex = 0 THEN '女' ELSE '未知' END AS sexStr from xxx group by sex where status = 0
返回结果是一个list, 里面的map key是查询的属性名, value是参数值。伪代码示意:
list[0]
map[0] (sex=1) map[1] (num=5) map[2] (sexStr=男)
list[1]
map[0] (sex=1) map[1] (num=5) map[2] (sexStr=男)
示例二(代码)
SELECT * FROM t_employee WHERE DATE_FORMAT(birthday,'%Y-%m-%d')>='1993-02-09' AND DATE_FORMAT(birthday,'%Y-%m-%d')<='1994-04-09' AND NAME LIKE '李%'
执行SQL
/**
* 查询姓李的,并且出生日期范围是1993-02-09到1994-04-09的员工
* sql:SELECT * FROM t_employee WHERE DATE_FORMAT(birthday,'%Y-%m-%d')>='1993-02-09' AND DATE_FORMAT(birthday,'%Y-%m-%d')<='1994-04-09' AND NAME LIKE '李%'
*/
@Test
public void selectByQueryWrapper3(){
QueryWrapper queryWrapper=new QueryWrapper();
// QueryWrapper queryWrapper2=Wrappers.query();
queryWrapper.apply("DATE_FORMAT(birthday,'%Y-%m-%d')>={0} and DATE_FORMAT(birthday,'%Y-%m-%d')<={1}","1993-02-09","1994-04-09").likeRight("name","李");
List employeeList = employeeMapper.selectList(queryWrapper);
System.out.println(employeeList);
}
sql实现:
SELECT * FROM t_employee WHERE NAME LIKE '李%' OR (email IS NOT NULL AND gender ='女')
mp实现:
/**
* 查询姓李的或者邮箱不为空并且是女性的员工
* sql:SELECT * FROM t_employee WHERE NAME LIKE '李%' OR (email IS NOT NULL AND gender ='女')
*/
@Test
public void selectByQueryWrapper4(){
QueryWrapper queryWrapper=new QueryWrapper();
// QueryWrapper queryWrapper2=Wrappers.query();
queryWrapper.likeRight("name","李").or(wq->wq.isNotNull("email").eq("gender","女"));
List employeeList = employeeMapper.selectList(queryWrapper);
System.out.println(employeeList);
}
案例三
查询姓李的并且邮箱不为空或者是女性的员工
sql实现:
SELECT * FROM t_employee WHERE NAME LIKE '李%' AND (email IS NOT NULL OR gender ='女')
mp实现:
/**
* 查询姓李的并且邮箱不为空或者是女性的员工
* sql:SELECT * FROM t_employee WHERE NAME LIKE '李%' AND (email IS NOT NULL OR gender ='女')
*/
@Test
public void selectByQueryWrapper5(){
QueryWrapper queryWrapper=new QueryWrapper();
// QueryWrapper queryWrapper2=Wrappers.query();
queryWrapper.likeRight("name","李").and(wq->wq.isNotNull("email").or().eq("gender","女"));
List employeeList = employeeMapper.selectList(queryWrapper);
System.out.println(employeeList);
}
案例四
查询属于编号1,2,3部门的并且薪水小于等于3500的员工 根据年龄从大到小排序显示
sql实现:
SELECT * FROM t_employee WHERE salary<=3500 AND departmentId IN (1,2,3) ORDER BY birthday ASC
mp实现:
/**
* 查询属于编号1,2,3部门的并且薪水小于等于3500的员工 根据年龄从大到小排序显示
* sql:SELECT * FROM t_employee WHERE salary<=3500 AND departmentId IN (1,2,3) ORDER BY birthday ASC
*/
@Test
public void selectByQueryWrapper6(){
QueryWrapper queryWrapper=new QueryWrapper();
// QueryWrapper queryWrapper2=Wrappers.query();
queryWrapper.likeRight("name","李").and(wq->wq.isNotNull("email").or().eq("gender","女"));
List employeeList = employeeMapper.selectList(queryWrapper);
System.out.println(employeeList);
}