如何从postgresql数据库中删除

Question

let total = req.body.Details.length;
  for (let i = 0; i < total; i++) {
  db.query('INSERT INTO position(unit,fulltime,user_id) values($1,$2,$3)'[req.body.Details[i].unit,req.body.Details[i].fulltime,companyuser.rows[0]._id],function(err,data){
    if (err) return callback(new Error(err));
    console.log('added')                            
  }) 
}

这里我可以将数组值插入数据库，数组如下：

"Details":[{"unit":"pqr","fulltime":"true"},{"unit":"abc","fulltime":"false"},{"unit":"xyz","fulltime":"true"}]

它来自邮递员。

let total = req.body.Details.length;
for (let i = 0; i < total; i++) {
 db.query('DELETE FROM position WHERE unit != ($1) AND user_id = $2',[req.body.Details[i].unit, companyuser.rows[0]._id],function(err,data){
  if (err) return callback(new Error(err));
  console.log('deleted')                            
 }) 
}

在更新时，如果我仅将unit更新为abc "Details":[{"unit":"abc"}]，则需要从数据库中删除prq and xyz。但是这个删除查询只删除了pqr我在哪里错了？