QueryWrapper条件构造之apply、last、select
场景： 查询数据库限制条数时
mysql上的limit使用
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QueryWrapper needSyn = new QueryWrapper();needSyn.ge("ModifyDate",lmtSynRec.getLatestDate());needSyn.last("limit 200");List<CusCarInfo> needData = cusCarInfoMapper.selectList(needSyn); |
如果是oracle则可以用apply
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needSyn.apply("rownum < {0}" , 200); |
如果是sqlserver
建议自己写sql查询语句
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<select id="getSynList" resultType="com.xmeport.project.model.entity.CusCarInfo"> select top ${top} * from CUS_CAR_INFO t where t.ModifyDate > cast(#{latestDate} as datetime) orderBy t.ModifyDate asc</select>List<CusCarInfo> getSynList(int top, Date latestDate); |
或者使用QueryWrapper的select
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QueryWrapper<CusCarInfo> wrapper = new QueryWrapper();wrapper.select("top 200 *");return this.list(wrapper); |
以上就是根据最新时间查询top条数据
传入的字段是时间类型，就用#{} 占位符接收。如果是具体的一个数字或字符可以用 ${ }来接收。
条件构造器QueryWrapper实例
我们再搞几个实例来深入理解下条件构造器QueryWrapper的用法：
案例一
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实现：
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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%' |
mp实现：
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/** * 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%' */@Testpublic void selectByQueryWrapper3(){ QueryWrapper<Employee> queryWrapper=new QueryWrapper(); // QueryWrapper<Employee> queryWrapper2=Wrappers.<Employee>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<Employee> employeeList = employeeMapper.selectList(queryWrapper); System.out.println(employeeList);} |
案例二
查询姓李的或者邮箱不为空并且是女性的员工
sql实现：
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SELECT * FROM t_employee WHERE NAME LIKE '李%' OR (email IS NOT NULL AND gender ='女') |
mp实现：
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/** * 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') */@Testpublic void selectByQueryWrapper4(){ QueryWrapper<Employee> queryWrapper=new QueryWrapper(); // QueryWrapper<Employee> queryWrapper2=Wrappers.<Employee>query(); queryWrapper.likeRight("name","李").or(wq->wq.isNotNull("email").eq("gender","女")); List<Employee> 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：
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SELECT * FROM t_employee WHERE NAME LIKE '李%' AND (email IS NOT NULL OR gender ='女') |
mp实现：
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/** * 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') */@Testpublic void selectByQueryWrapper5(){ QueryWrapper<Employee> queryWrapper=new QueryWrapper(); // QueryWrapper<Employee> queryWrapper2=Wrappers.<Employee>query(); queryWrapper.likeRight("name","李").and(wq->wq.isNotNull("email").or().eq("gender","女")); List<Employee> 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：
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SELECT * FROM t_employee WHERE salary<=3500 AND departmentId IN (1,2,3) ORDER BY birthday ASC |
mp实现：
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/** * 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 */@Testpublic void selectByQueryWrapper6(){ QueryWrapper<Employee> queryWrapper=new QueryWrapper(); // QueryWrapper<Employee> queryWrapper2=Wrappers.<Employee>query(); queryWrapper.likeRight("name","李").and(wq->wq.isNotNull("email").or().eq("gender","女")); List<Employee> employeeList = employeeMapper.selectList(queryWrapper); System.out.println(employeeList);} |
以上为个人经验，希望能给大家一个参考，也希望大家多多支持服务器之家。
原文链接：https://blog.csdn.net/u012078155/article/details/106760123
