I have a native query
searchSql = "Select firstname,lastname from students order by id desc"
and then i do
Query query = entityManager.createNativeQuery(searchSql);
List<Map<String, Object>> results = query.getResultList();
Now if i print the results with KEYS
List<String>headers = new ArrayList<>();
for(String header : results.get(0).keySet()){
headers.add(header);
}
i get random order of the column names.
How can i get the exact order as in the select statement ?
LinkedHashMap should be the answer but i get class cast exceptions... Any generic ideas?
I checked if LinkedHashMap causes the randomness of columns:
#Test
public void linkedHashMap() {
Map<String, Integer> map = new LinkedHashMap<>();
IntStream.range(0, 10).forEach(integer -> {
map.put(
String.valueOf(integer),
integer
);
});
for (String val : map.keySet()){
System.out.println(val);
}
}
but instead it prints:
0
1
2
3
4
5
6
7
8
9
The randomness seems to be a limitation of Hibernate, as stated here
If simply changing the signature to List<Object[]> results = query.getResultList(); does NOT work, then you can give a shot at SqlResultSetMapping. That way, the implicit map insertion would be avoided and order would be maintained I guess (I am not 100% sure, needs to be tested)
See https://docs.oracle.com/javaee/7/api/javax/persistence/SqlResultSetMapping.html.
Related
What is the ordering of the keys in an Ignite cache (without using indexing) and is it possible to do the equivalent of the following RocksDB snippet
try (final RocksIterator rocksIterator =
rocksDB.newIterator(columnFamilyHandleList.get(1))) {
for (rocksIterator.seek(prefixKey);
i.e. jump to the next entry starting with a given byte[] or String?
The way you'd do that in Ignite is by using SQL.
var query = new SqlFieldsQuery("select x,y,z from table where z like ? order by x").setArgs("prefix%");
try (var cursor = cache.query(query)) {
for (var r : cursor) {
Long id = (Long) r.get(0);
BigDecimal value = (BigDecimal) r.get(1);
String name = (String) r.get(2);
}
}
Good Morning,
I have the following table:
_____________________
Name Status Num
A Good 6
B Bad 6
C Bad 7
I want to select all rows where "Status = 'Good' AND Num = '6'" OR "Status = 'Bad' AND Num = '7'"
So I would select rows with Names A and C from the above reference data.
I am hoping to be able to pass in two equal sized lists (ordered in the way I desire the query to be constructed), but have been unable to figure this out. The standard queries (SelectXByStatusAndNum) query generates SQL using 'IN' statements, and returns all 3 rows in the above data instead of just two.
Any insight appreciated
I believe the best way is to use a #Query annotation in the repository:
#Entity
#Table(name = "table_name")
public class TableName {
#Id
#Basic(optional = false)
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "ID")
private Long id;
#Column(name = "name")
private String name;
#Column(name = "status")
private String status;
#Column(name = "num")
private Integer num;
/**
* getters/setters, etc
**/
public interface TableNameRepository extends CrudRepository<TableName, Long> {
#Query("select t from TableName t where (status = :status1 and num = :num1 or status = :status2 and num = :num2)")
List<TableName> findByStatusAndNumOrStatusAndNum(#Param("status1") String status1,
#Param("num1") Integer num1, #Param("status2") String status2, #Param("num2") Integer num2);
}
It's a way to get values for a given parameters. In case of collections as parameters there is no in-box case due to RDBMS concept. You just can write some java code based on the key-valued parameter and collect results:
public interface TableNameRepository extends CrudRepository<TableName, Long> {
List<TableName> findByStatusAndNumIn(String status, Collection<Integer> nums);
}
List<TableName> result = new ArrayList<>();
List<TableName> itemGood = findByStatusAndNumIn("Good", numsGood);
List<TableName> itemBad = findByStatusAndNumIn("Bad", numsBad);
result.addAll(itemGood);
result.addAll(itemBad);
Instead of equal size lists, I suggest creating an object with both status and num and provide a list of those - I called it CustomCriteria below. Since there is no straightforward way to handle this with standard spring data query methods I believe the best way is to do this with criteria builder in a custom repository that builds the list of OR's from a list of AND predicates based on the criteria entries in the provided list. For example:
public List<YourTable> findMatching(List<CustomCriteria> customCriteriaList) {
CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
CriteriaQuery<YourTable> criteriaQuery = criteriaBuilder.createQuery(YourTable.class);
Root<YourTable> itemRoot = criteriaQuery.from(YourTable.class);
List<Predicate> predicates = new ArrayList<>(customCriteriaList.size());
for (CustomCriteria customCriteria : customCriteriaList) {
Predicate predicateForNum
= criteriaBuilder.equal(itemRoot.get("num"), customCriteria.getNum());
Predicate predicateForStatus
= criteriaBuilder.equal(itemRoot.get("status"), customCriteria.getStatus());
predicates.add(criteriaBuilder.and(predicateForNum, predicateForStatus));
}
Predicate finalPredicate = criteriaBuilder.or(predicates.toArray(new Predicate[predicates.size()]));
criteriaQuery.where(finalPredicate);
return entityManager.createQuery(criteriaQuery).getResultList();
}
let's assume that i have a table with columns such as:
ID SSID BSSID RSSI
1 abcd hs:hd:sd -60
2 abcd hs:hd:po -68
There are about 5000 records with the same SSID, slighltly different BSSID and the LEVEL values. My device is scanning the nearest environment for WiFi networks, therefore I know their MAC address and level of RSSI. I pick 3 with the highest value od RSSI.
First thing I would like to know if it is possible to search through the database to get all the records with the LEVEL value equal or close to 60, for instance 59,58,61.
Secondly, is there a way to query the database to return all the records with the same MAC addresses and RSSI values as from the 3 best scan result? If so, how would that query look like?
EDIT: Thanks for all the answers. What I'm trying to do now is to compare 3 scans with records stored in database with getRequiredData function. I would like to pass 2 parameters to this function, mac address and level and find records with same value for both parameters. The rawQuery seems to be fine, code is compiling but the app is crashing with the first scan. I cant find the cause of it, is it because my logic of getting these parameters is wrong or does it have something to do with query?
public Cursor getRequiredData(String mac, int level){
SQLiteDatabase db = this.getWritableDatabase();
Cursor res = db.rawQuery("SELECT BSSID, RSSI FROM TABLE_NAME WHERE BSSID =? AND RSSI=?", new String[] {mac, level});
return res;
}
scan part:
class WifiReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
sb = new StringBuilder();
Comparator<ScanResult> comparator = new Comparator<ScanResult>() {
#Override
public int compare(ScanResult o1, ScanResult o2) {
return (o1.level>o2.level ? -1 : (o1.level==o2.level ? 0 : 1));
}
};
lista = wifiManager.getScanResults();
Collections.sort(lista, comparator);
for (int i = 0; i < lista.size(); i++) {
scanResult = wifiManager.getScanResults().get(i);
sb.append(new Integer(i + 1).toString() + ". " + (lista.get(i)).SSID + " " + (lista.get(i)).BSSID + " " + (lista.get(i)).level + "\n");
boolean isInserted = myDb.insertData(lista.get(i).SSID.toString(), lista.get(i).BSSID.toString(), lista.get(i).level);
if (isInserted = true)
Toast.makeText(MainActivity.this, "Data inserted", Toast.LENGTH_LONG).show();
else
Toast.makeText(MainActivity.this, "Data not inserted", Toast.LENGTH_LONG).show();
}
for (int i=0; i<4; i++)
{
scanResult = wifiManager.getScanResults().get(i);
match = myDb.getRequiredData(lista.get(i).BSSID.toString(), lista.get(i).level);
}
Log.i("match values: ", DatabaseUtils.dumpCursorToString(match));
txt.setText(sb);
wifiManager.startScan();
}
}
Here is what match contains:
2018-12-10 16:36:26.334 13347-13347/com.example.maciek.wifiscann I/match values:: >>>>> Dumping cursor android.database.sqlite.SQLiteCursor#e1a86d1
0 {
BSSID=f4:c5:ed:5c:s6:20
RSSI=-69
}
1 {
BSSID=f4:c5:ed:5c:s6:20
RSSI=-69
}
2 {
BSSID=f4:c5:ed:5c:s6:20
RSSI=-69
}
3 {
BSSID=f4:c5:ed:5c:s6:20
RSSI=-69
}
4 {
BSSID=f4:c5:ed:5c:s6:20
RSSI=-69
}
5 {
BSSID=f4:c5:ed:5c:s6:20
RSSI=-69
}
<<<<<
To get the 3 rows with the closest values to 60 in column LEVEL:
SELECT * FROM tablename ORDER BY ABS(LEVEL - 60), LEVEL LIMIT 3
For the 2nd part of your question, you should provide sample data of the table. Edit:
From the sample data that you posted I don't see a column RSSI, but if it exists in the table then the SELECT statement is ok.
Change the 2nd parameter of rawQuery() to:
new String[] {mac, String.valueOf(level)}
because level is int.
In onReceive() you use myDb. I don't know how you initialize it.
If the app crashes you must copy the log, the part that identifies the problem and post it.
First thing I would like to know if it is possible to search through
the database to get all the records with the LEVEL value equal or
close to 60, for instance 59,58,61.
SELECT * FROM your_table WHERE level BETWEEN 59 AND 61;
where your_table is the respective table name.
Note if levels are negative (as per example data) then BETWEEN requires the lowest value first so it would be BETWEEN -61 AND -59.
Secondly, is there a way to query the database to return all the
records with the same MAC addresses and RSSI values as from the 3 best
scan result? If so, how would that query look like?
SELECT * FROM your_table WHERE your_mac_address_column = 'the_mac_address_value' AND RSSI = 'the_rssi_value' ORDER BY LEVEL DESC LIMIT 3
Note the above assumes that the MAC address is stored in a column (if NOT then cannot be done unless the mac address can be correlated to a column).
Assumes best LEVEL is lowest so -1 is better than -60 (if not then use ASC instead of DESC)
Again your_table, your_mac_address_column, the_mac_address_value and the_rssi_value would be replaced accordingly with actual values (note that strings should be in single quotes).
I have two classes:
public class ClassOne {
private String id;
private String name;
private String school;
private String score; //Default score is null
..getters and setters..
}
public class ClassTwo {
private String id;
private String marks;
..getters and setters..
}
And, I have two Lists of the above classes,
List<ClassOne> listOne;
List<ClassTwo> listTwo;
How can I compare two list and assign marks from listTwo to score of listOne based on the criteria if the IDs are equal. I know, we can use two for loops and do it. But I want to implement it using Java8 streams.
List<ClassOne> result = new ArrayList<>();
for(ClassOne one : listOne) {
for(ClassTwo two : listTwo) {
if(one.getId().equals(two.getId())) {
one.setScore(two.getmarks());
result.add(one);
}
}
}
return result;
How can I implement this using Java8 lambda and streams?
Let listOne.size() is N and listTwo.size() is M.
Then 2-for-loops solution has complexity of O(M*N).
We can reduce it to O(M+N) by indexing listTwo by ids.
Case 1 - assuming listTwo has no objects with the same id
// pair each id with its marks
Map<String, String> marksIndex = listTwo.stream().collect(Collectors.toMap(ObjectTwo::getId, ObjectTwo::getMarks));
// go through list of `ObjectOne`s and lookup marks in the index
listOne.forEach(o1 -> o1.setScore(marksIndex.get(o1.getId())));
Case 2 - assuming listTwo has objects with the same id
final Map<String, List<ObjectTwo>> marksIndex = listTwo.stream()
.collect(Collectors.groupingBy(ObjectTwo::getId, Collectors.toList()));
final List<ObjectOne> result = listOne.stream()
.flatMap(o1 -> marksIndex.get(o1.getId()).stream().map(o2 -> {
// make a copy of ObjectOne instance to avoid overwriting scores
ObjectOne copy = copy(o1);
copy.setScore(o2.getMarks());
return copy;
}))
.collect(Collectors.toList());
To implement copy method you either need to create a new object and copy fields one by one, but in such cases I prefer to follow the Builder pattern. It also results in more "functional" code.
Following code copies marks from ObjectTwo to score in ObjectOne, if both ids are equal, it doesn't have intermediate object List<ObjectOne> result
listOne.stream()
.forEach(one -> {listTwo.stream()
.filter(two -> {return two.getId().equals(one.getId());})
.limit(1)
.forEach(two -> {one.setScore(two.getMarks());});
});
This should work.
Map<String, String> collect = listTwo.stream().collect(Collectors.toMap(ObjectTwo::getId, ObjectTwo::getMarks));
listOne
.stream()
.filter(item -> collect.containsKey(item.getId()))
.forEach(item -> item.setScore(collect.get(item.getId())));
Using Dapper-dot-net...
The following yields no results in the data object:
var data = conn.Query(#"
select top 25
Term as Label,
Type,
ID
from SearchTerms
WHERE Term like '%#T%'",
new { T = (string)term });
However, when I just use a regular String Format like:
string QueryString = String.Format("select top 25 Term as Label, Type, ID from SearchTerms WHERE Term like '%{0}%'", term);
var data = conn.Query(QueryString);
I get 25 rows back in the collection. Is Dapper not correctly parsing the end of the parameter #T?
Try:
term = "whateverterm";
var encodeForLike = term => term.Replace("[", "[[]").Replace("%", "[%]");
string term = "%" + encodeForLike(term) + "%";
var data = conn.Query(#"
select top 25
Term as Label,
Type,
ID
from SearchTerms
WHERE Term like #term",
new { term });
There is nothing special about like operators, you never want your params inside string literals, they will not work, instead they will be interpreted as a string.
note
The hard-coded example in your second snippet is strongly discouraged, besides being a huge problem with sql injection, it can cause dapper to leak.
caveat
Any like match that is leading with a wildcard is not SARGable, which means it is slow and will require an index scan.
Yes it does. This simple solution has worked for me everytime:
db.Query<Remitente>("SELECT *
FROM Remitentes
WHERE Nombre LIKE #n", new { n = "%" + nombre + "%" })
.ToList();
Best way to use this to add concat function in query as it save in sql injecting as well, but concat function is only support above than sql 2012
string query = "SELECT * from country WHERE Name LIKE CONCAT('%',#name,'%');"
var results = connection.query<country>(query, new {name});
The answer from Sam wasn't working for me so after some testing I came up with using the SQLite CONCAT equivalent which seems to work:
string sql = "SELECT * FROM myTable WHERE Name LIKE '%' || #NAME || '%'";
var data = IEnumerable data = conn.Query(sql, new { NAME = Name });
Just to digress on Sam's answer, here is how I created two helper methods to make searches a bit easier using the LIKE operator.
First, creating a method for generating a parameterized query, this method uses dynamic: , but creating a strongly typed generic method should be more desired in many cases where you want static typing instead of dynamic.
public static dynamic ParameterizedQuery(this IDbConnection connection, string sql, Dictionary<string, object> parametersDictionary)
{
if (string.IsNullOrEmpty(sql))
{
return null;
}
string missingParameters = string.Empty;
foreach (var item in parametersDictionary)
{
if (!sql.Contains(item.Key))
{
missingParameters += $"Missing parameter: {item.Key}";
}
}
if (!string.IsNullOrEmpty(missingParameters))
{
throw new ArgumentException($"Parameterized query failed. {missingParameters}");
}
var parameters = new DynamicParameters(parametersDictionary);
return connection.Query(sql, parameters);
}
Then adding a method to create a Like search term that will work with Dapper.
public static string Like(string searchTerm)
{
if (string.IsNullOrEmpty(searchTerm))
{
return null;
}
Func<string, string> encodeForLike = searchTerm => searchTerm.Replace("[", "[[]").Replace("%", "[%]");
return $"%{encodeForLike(searchTerm)}%";
}
Example usage:
var sql = $"select * from products where ProductName like #ProdName";
var herringsInNorthwindDb = connection.ParameterizedQuery(sql, new Dictionary<string, object> { { "#ProdName", Like("sild") } });
foreach (var herring in herringsInNorthwindDb)
{
Console.WriteLine($"{herring.ProductName}");
}
And we get our sample data from Northwind DB:
I like this approach, since we get helper extension methods to do repetitive work.
My solution simple to this problem :
parameter.Add("#nomeCliente", dfNomeCliPesquisa.Text.ToUpper());
query = "SELECT * FROM cadastrocliente WHERE upper(nome) LIKE " + "'%" + dfNomeCliPesquisa.Text.ToUpper() + "%'";