class).in(StuSubRelation::getStuId, stuIds); // 通过学生ID查询课程分数 List<StuSubRelation> stuSubRelations = stuSubRelationMapper.selectList(wrapper); // 批量查询课程ID Set<Integer> subIds = stuSubRelations.stream().map(St
stuIds);//通过学生ID查询课程分数List<StuSubRelation> stuSubRelations =stuSubRelationMapper.selectList(wrapper);//批量查询课程IDSet<Integer> subIds =stuSubRelations.stream().map(StuSubRelation::getSubId).collect(toSet());if(stuIds.size() > 0 && subIds.size() ...
("One record is expected, but the query result is multiple records"); } return ts.get(0); } return null; } /** * 根据 Wrapper 条件,判断是否存在记录 * * @param queryWrapper 实体对象封装操作类 * @return */ default boolean exists(Wrapper<T> queryWrapper) { Long count = this.select...
lambdaQuery(StuSubRelation.class).eq(StuSubRelation::getStuId, stuId); // 查询匹配关系 List<StuSubRelation> stuSubRelations = stuSubRelationMapper.selectList(wrapper); Set<Integer> subIds = stuSubRelations.stream().map(StuSubRelation::getSubId).collect(toSet()); if (studentVo != null &&...
SUBDATE(d,n)日期 d 减去 n 天后的日期 SELECT SUBDATE('2011-11-11 11:11:11', 1) ->2011-11-10 11:11:11 (默认是天) SUBTIME(t,n)时间 t 减去 n 秒的时间 SELECT SUBTIME('2011-11-11 11:11:11', 5) ->2011-11-11 11:11:06 (秒) SYSDATE()返回当前日期和时间 SELECT SYSDATE() ...
subJoin.getJoinList().forEach(this::processJoin); } if (subJoin.getLeft() != null) { processFromItem(subJoin.getLeft()); } } else if (fromItem instanceof SubSelect) { SubSelect subSelect = (SubSelect) fromItem; if (subSelect.getSelectBody() != null) { ...
LambdaQueryWrapper<StuSubRelation> wrapper = Wrappers.lambdaQuery(StuSubRelation.class).eq(StuSubRelation::getStuId, stuId); // 查询匹配关系 List<StuSubRelation> stuSubRelations = stuSubRelationMapper.selectList(wrapper); Set<Integer> subIds = stuSubRelations.stream().map(StuSubRelation::getSubId...
MyISM:不支持事务,不支持行锁和外键约束,插入和更新时锁定全表,效率低。MyISM保存表行数,执行select不扫描全表。读操作较多时建议MyISM。 Mysql行级锁和表锁? MyISM只支持表锁,InnoDB支持行锁和表锁。 表锁:开销小,加锁快。锁力度大,死锁概率高,并发量低。
selectk.*,p.st_name_idfromxg_ks_stuk leftjoinxg_ks_pcp onk.pc_id=p.id where k.xs_id=#{xsId} </select> <resultMapid="myExamMap"type="org.stu.exam.vo.MyExamVo"> <associationproperty="exam"resultMap="examMap"></association> ...
select * from t_goods <where> <if test="categoryId != null"> and category_id = #{categoryId} </if> <if test="currentPrice != null"> and current_price < #{currentPrice} </if> </where> </select> 1. 2. 3. 4. 5.