mysql中EXISTS和IN的使用方法比较

select a.batchName,a.projectId from ucsc_project_batch a where EXISTS (select b.id from ucsc_project b where a.projectId = b.id)

select a.batchName,a.projectId from ucsc_project_batch a where EXISTS (select b.companyId,b.name from ucsc_project b where a.projectId = b.id)

select a.batchName,a.projectId from ucsc_project_batch a where a.projectId in (select b.id from ucsc_project b)

select a.batchName,a.projectId from ucsc_project_batch a where EXISTS (select b.id from ucsc_project b)

select a.batchName,a.projectId from ucsc_project_batch a where EXISTS (select b.id from ucsc_project b where b.id is null)

select a.batchName,a.projectId from ucsc_project_batch a where a.projectId in (select b.id from ucsc_project b)

$result = [];
$ucsc_project_batch = "select a.batchName,a.projectId from ucsc_project_batch a";
$ucsc_project = "select b.id from ucsc_project b";
for($i = 0;$i < $ucsc_project_batch .length;$i++){
 for($j = 0;$j < $ucsc_project .length;$j++){
  if($ucsc_project_batch [$i].projectId== $ucsc_project [$j].id){
   $result[] = $ucsc_project_batch [$i];
   break;
  }
 }
}

select a.batchName,a.projectId from ucsc_project_batch a where EXISTS (select b.id from ucsc_project b where a.projectId = b.id)

$result = [];
$ucsc_project_batch = "select a.batchName,a.projectId from ucsc_project_batch a ";
for ($i = 0; $i < $ucsc_project_batch . length; $i++) {
 if (exists($ucsc_project_batch [$i] . projectId)) {//执行select b.id from ucsc_project b where a.projectId=b.id        
  $result[] = $ucsc_project_batch [$i];
 }
}