MP的双表合并查询

1、双表合并查询

/两表合并/
public void te() {

/全选/
List modelEntities = modelDao.selectList(null);
List modelControlVos = new ArrayList<>();

/将查询得到的数据赋值给modelControlVos/
modelControlVos = modelEntities.stream().map(modelEntity -> {
ModelControlVo modelControlVo = new ModelControlVo();
modelControlVo.setModelId(modelEntity.getModelId());
modelControlVo.setModelName(modelEntity.getModelName());
modelControlVo.setModelType(modelEntity.getModelType());
return modelControlVo;

}).collect(Collectors.toList());

/获得所有的modelId并去重/
Set modelIdSet = modelEntities.stream().map(modelEntity -> {
return modelEntity.getModelId();
}).collect(toSet());
/判断取出来的模型表有数据/
if (modelIdSet.size() > 0) {
/条件查询得到分数表的数据/
LambdaQueryWrapper wrapper = Wrappers.lambdaQuery();
wrapper.in(JssChainModelScore::getModelId, modelIdSet);

/如果只要某一个属性，可以select/
/wrapper.in(JssChainModelScore::getModelId, modelIdSet).select(JssChainModelScore::getModelId);/
List jssChainModelScores = jssChainModelScoreDao.selectList(wrapper);

/取出它的模型名和它本身作为map/
Map<String, JssChainModelScore> jssChainModelScoreMap = jssChainModelScores.stream().collect(Collectors.toMap(JssChainModelScore::getModelId, p -> p));

/遍历赋值/
for (ModelControlVo modelControlVo : modelControlVos) {
JssChainModelScore jssChainModelScore = jssChainModelScoreMap.get(modelControlVo.getModelId());
if (jssChainModelScore!=null){
modelControlVo.setSynthesisAVGScore(jssChainModelScore.getSynthesisScore());
}
}
}

2、双表合并查询-分页
在查询合并后，加入分页

int pageSize = 2;
int pageNo=3;
int total = modelControlVos.size();
int pafeSum = (total+pageSize-1)/pageSize;
List subList = modelControlVos.stream().skip((pageNo-1)*pageSize).limit(pageSize).collect(Collectors.toList());

3、一对一查询合并

/单表合并/
@Test
public void getOneMerge(){
int Id = 1;
LambdaQueryWrapper wrapper = Wrappers.lambdaQuery();
wrapper.eq(CollectEntity::getId,Id);

// 先查询用户信息
CollectEntity collectEntity = collectDao.selectOne(wrapper);

DetailEntity detailEntity = new DetailEntity();
detailEntity.setCollectId(collectEntity.getId());
System.out.println(detailEntity.toString());

}