Am not a learner to boolean expressions but this seems to be giving me a bit of an headache.
In my app when i search for a user,I am recieving certain values from my datase using this MYSQL statement.
SELECT `u3`.`username`,
CASE WHEN `u3`.`username` IS NULL THEN 'Not Existing'
ELSE 'Existing' END is_following
FROM `userinfo` `u3` WHERE `u3`.`username` LIKE '%".mysql_real_escape_string($data)."%' OR `u3`.`email` LIKE '%".mysql_real_escape_string($data)."%'
UNION
SELECT `u2`.`username`,
CASE WHEN `u2`.`username` IS NULL THEN 'Follow'
ELSE 'Following' END is_following
FROM
`userinfo` `u1` LEFT JOIN `followers` `f`
ON `u1`.`username` = `f`.`source_id`
LEFT JOIN `userinfo` `u2`
ON `f`.`destination_id` = `u2`.`username`
AND (`u2`.`username` LIKE '%".mysql_real_escape_string($data)."%' OR `u2`.`email` LIKE '%".mysql_real_escape_string($data)."%')
WHERE
`u1`.`username` = '$name'
Now the syntax above would return these set of values, a username and My own metadata. For example it would return
set of values 1: (davies and Existing)[if davies is in the userinfo table] AND (davies and Following)[if davies is following halex in the followers table]
OR
set of values 2: (null and Not Existing)[if davies is not in the userinfo table] AND (null and not followed)[davies does not exist]
OR
set of values 3: (davies and Existing)[if davies is in the userinfo table] AND (null and Not Following)[if davies is not following halex]
These are the set of values i recieve and i need an if statement to sieve through so i can display to my users this simple information
davies and Following OR davies and Follow[if davies is not following halex] OR User Does not Exist
Now am not sure if i should change the structure of my SOL statement or i could get a better way of handling this logic with if and else statements
This was the structure of my if else statement but it doesn't seem to work the way i want it to
if(username != null && metadata.contains("Existing"))//user exist
{
value = username;
//user exists but skip
}else
{
if(username != null)
{
map = new HashMap<String, String>();
map.put(TAG_USERNAME, value);
map.put(TAG_METADATA, metadata);
listvalue.add(map);
}else
{
//user does not exist
Log.i("search ", "user does not exist");
}
}
The codes above belongs to android.
Thanks any suggestion is appreciated. Thanks again in Advance.
What if you split your query into two parts? Querying for one set of information at a time will make things simpler and easier to debug.
I could imagine doing something that looks like this (in pseudo-code):
query = "SELECT username
FROM `userinfo` `u3`
WHERE `u3`.`username` LIKE '%".mysql_real_escape_string($data)."%'
OR `u3`.`email` LIKE '%".mysql_real_escape_string($data)."%'"
var result = db.execute(query);
// set to true if the above query returns at least one row
bool user_exists = (result.RowCount() > 0)
var username = (user_exists)? result.GetRow().GetField("username") : null;
if(user_exists)//user exist
{
value = username;
//user exists but skip
} // ....
(I've only replicated the functionality pertaining to your UNION's first SELECT statement; the logic associated with the second statement can be similarly rewritten.)
Related
I have a collection where I store user groups. Each group has a group name, group limit and an array of users ID's.
I wonder how the best way to retrieve one group details and then users details, like name, photo, etc.
Right now, I am doing two queries to the database. First retrieving the group data(name, etc), second getting a list of users who has in the user details the information of the group ID:
"syncDesp = a4sQ27xb1wuD2rhONU2K"
I'm afraid of calling the database to many times.
// Get Group details
Preferencias prefs = new Preferencias(view.getContext());
listenGroups = pFirestore.collection("syncDesps").document(prefs.getSyncDesp()).addSnapshotListener((documentSnapshot, e) -> {
if(e != null){
Log.i("dados erro", Objects.requireNonNull(e).getMessage());
}
if(documentSnapshot != null){
String nomeGrupo = Objects.requireNonNull(documentSnapshot.get("nomeGrupo")).toString();
textNomeGrupo.setText(nomeGrupo);
ArrayList membrosGrupo = (ArrayList) Objects.requireNonNull(documentSnapshot.get("syncDesp"));
}
});
// Get User Details
FirebaseFirestore grupoFire = FirebaseFirestore.getInstance();
grupoFire.collection("usuarios")
.whereEqualTo("syncDesp", prefs.getSyncDesp())
.addSnapshotListener((queryDocumentSnapshots, e1) -> {
listaUsuarios.clear();
if(e != null){
Log.i("dados erro", Objects.requireNonNull(e1).getMessage());
}
for(DocumentSnapshot usuarioSnapshot : Objects.requireNonNull(queryDocumentSnapshots).getDocuments()){
String idU = (usuarioSnapshot.get("id") == null) ? "" : Objects.requireNonNull(usuarioSnapshot.get("id")).toString();
String nomeUsuario = (usuarioSnapshot.get("nome") == null) ? "" : Objects.requireNonNull(usuarioSnapshot.get("nome")).toString();
String fotoUsuario = (usuarioSnapshot.get("imgUsuario") == null) ? "" : Objects.requireNonNull(usuarioSnapshot.get("imgUsuario")).toString();
UsuarioMeuGrupo usuarioMeuGrupo = new UsuarioMeuGrupo();//
usuarioMeuGrupo.setIdUsuario(idU);
usuarioMeuGrupo.setNome(nomeUsuario);
usuarioMeuGrupo.setFoto(fotoUsuario);
listaUsuarios.add(usuarioMeuGrupo);
}
adaptera.setOnItemClickRemoverListener(uMeuGrupo -> {
Log.i("dados uMeuGrupo Clic", uMeuGrupo.getNome());
});
adaptera.notifyDataSetChanged();
});
I wonder if I should query the group collection separately from the users collection or if there is a way of making only one function to retrieve data from both collections.
It's not possible to make a single query in Cloud Firestore span multiple collections. There is no join-like operation like you have in SQL. The only exception to this is collection group queries, which doesn't apply to your situation.
What you're doing right now is probably the best you can do with the database structure you have. If you want fewer queries, you'll have to do something to restructure your data to support that.
I have a database table in my android app. I want to compare database table name with a particular string.
Here is my code
if(branchName == TABLE_NAME)
{
}
else
{
Toast.makeText(this,"table not available",Toast.LENGTH_LONG).show();
}
Here branchName is the string.TABLE_NAME is a static string and it is the name of the table.
Whenever I run this code, control goes to else part and shows the toast message.
Why? How can I fix that?
for comparing two string you must use equal or equalsIgnoreCase ... ...
if (branchName.equalsIgnoreCase(TABLE_NAME) ){
// do sth
}
else{
Toast.makeText(this,"table not available",Toast.LENGTH_LONG).show();
}
try this way.
I want something like
objectid id name lastname pic
hx5w887 1 name1 lastname1 pic1
lops4wus 2 name2 lastname2 pic2
zh7w8sa 3 name3 lastname3 pic3
I don't want to change the objectId, just I want that field and every time I save an object increment in 1. I am searched a lot in google, about this, it is no possible at least you can something with Cloud Parse code, but I do not know how to make this function, I don't know if "Increment" can help me with this, and I do not know how to run the function anyway.
Parse.Cloud.afterSave("counter", function(request) {
var nameId = request.object.get("name").id;
var Name = Parse.Object.extend("Name");
var query = new Parse.Query(Name);
query.get(nameId).then(function(post) {
post.increment("idkey",+1);
post.save();
}, function(error) {
throw "Got an error " + error.code + " : " + error.message;
});
});
I deploy and
call the function in Android
ParseCloud.callFunctionInBackground("counter", new HashMap<String, Object>(), new FunctionCallback<String>() {
// #Override
public void done(String result, ParseException e) {
if (e == null) {
} else {
// handleError();
}
}
});
But nothing happens, what can be the problem? Sorry my bad english.
You can use ParseCloud 'beforeSave' functionality.
You can declare a code which will run before saving a new object of a specific class.
In this code you query for your class items, order it and get the first item (the highest value) then you can the next value (highest +1) to the new saved object.
For more info you can take a look at Parse documentation and in this thread (it is not in java but it is very similar)
EDIT: Since Parse is not longer is now an open source might be that things have changed.
i want to make a simple query, with multiple conditions
I use OrmLite to map entity object.
Now I want to search for an object into my table.
Supposing i have a Person entity that maps PERSON table, what I want to do is to initialize an object with some parameters and search it.
Suppose a function searchPerson(Person oPerson)
If i pass an object OPerson like this
Id = null
Name = John
Age = null
Sex = male
Is possible to write a query to reach that goal? Something like this pseudo-code
pers = (from p in db.Table<Person>()
where (if OPerson.Id !=null) p.Id==OPerson.Id}
AND {(if OPerson.Name !=null) p.Name.Contains(OPerson.Name)}
AND {(if condition) where-contion}
select p).ToList();
I know that i can do multiple query in this way
list=PersonDao.queryBuilder().where().eq("name",OPerson.name)
.and().eq("sex",OPerson.sex").query();
but I want also to check if the value exists
where (if OPerson.Id !=null) p.Id==OPerson.Id}
#ArghArgh is close but doesn't have the ANDs right. The problem is that the AND statements are conditional on whether there were any previous statements. I'd do something like:
QueryBuilder<Person, Integer> queryBuilder = dao.queryBuilder();
Where<Person, Integer> where = queryBuilder.where();
int condCount = 0;
if (oPerson.id != null) {
where.eq("id", oPerson.id);
condCount++;
}
if (oPerson.name != null) {
where.like("name", "%" + oPerson.name + "%");
condCount++;
}
...
// if we've added any conditions then and them all together
if (condCount > 0) {
where.and(condCount);
}
// do the query
List<Persion> personList = queryBuilder.query();
This makes use of the where.and(int) method which takes a number of clauses on the stack and puts them together with ANDs between.
I think that you must use the QueryBuilder.
Try something like this
QueryBuilder<Person, Integer> queryBuilder = PersonDao.queryBuilder();
// get the WHERE object to build our query
Where<Person, String> where = queryBuilder.where();
if(oPerson.Name!=null)
where.like("Name", "%"+oPerson.Name+"%");
// and
where.and();
if(Person.Sex!=null)
where.like("Sex", "%"+oPerson.sex+"%");
PreparedQuery<Person> preparedQuery = queryBuilder.prepare();
Than you can call it in this way
List<Person> list = PersontDao.query(preparedQuery);
I have two tables CustomerBalance and Customer which are bound with CustomerRefId field.
I want the CustomerBalance records that are lets say greater than 100 for a field balance of this tables. I also want to include into my results the name of the particular customer that fulfills that criteria. I created the following method that works!
public List<CustomerBalance> getCustomerBalanceFilter(String filterVal) {
try {
PreparedQuery<CustomerBalance> preparedQuery = mDbHelper.getCustomerBalanceDao().queryBuilder()
.where().gt(CustomerBalance.DB_COL_CUSTOMER_BALANCE, filterVal)
.prepare();
List<CustomerBalance> result = mDbHelper.getCustomerBalanceDao().query(preparedQuery);
for(CustomerBalance alert : result) {
PreparedQuery<Customer> getCustQuery = mDbHelper.getCustomerDao().queryBuilder()
.where().eq(Customer.DB_COL_CUSTOMER_REF_ID, alert.getCustomerID())
.prepare();
List<Customer> customer = mDbHelper.getCustomerDao().query(getCustQuery);
alert.setCustomer(customer.size() == 1 ? customer.get(0) : null);
}
return result;
} catch(Exception ex) {
return null;
}
}
This methods is working, is this the best way to write such a query? or is there a more appropriate approach?
One improvement to your query is to use ORMLite's SelectArg to pass in the customer-id instead of a new query each time. Something like:
...
List<CustomerBalance> result = mDbHelper.getCustomerBalanceDao()
.query(preparedQuery);
SelectArg custIdArg = new SelectArg();
PreparedQuery<Customer> getCustQuery = mDbHelper.getCustomerDao().queryBuilder()
.where().eq(Customer.DB_COL_CUSTOMER_REF_ID, custIdArg)
.prepare();
for (CustomerBalance alert : result) {
custIdArg.setValue(alert.getCustomerID());
List<Customer> customer = mDbHelper.getCustomerDao().query(getCustQuery);
alert.setCustomer(customer.size() == 1 ? customer.get(0) : null);
}
Here are the docs for SelectArg:
http://ormlite.com/docs/select-arg
FYI, there also is an UpdateBuilder, but I don't see an easy way to turn your code above into a single UPDATE statement.