In RDMS if I have to execute "Select emp_name from Employee where empid=100". I would do this,
String query = "Select emp_name from Employee where empid=100"
Statement stmt = DriverManager.getConnection(db, user, password).createStatement();
result = stmt.executeQuery(query);
How can I do the same in MongoDB where I get the query like "Employee.find({'empid:1000'},{emp_name:1})
Currently this is the code I'm using, in which I have to write the 'where' and 'select' part I mean dbObj(where) and projectdbObj(projecttion Or select part) separately.
DBObject dbObj = (DBObject) JSON.parse("{'employee.empid':'1000'}");
DBObject projectdbObj = (DBObject) JSON.parse("{'emp_name':1}");
try{
MongoCollection<Document> coll = mongoClient.getDatabase("Company" ).getCollection("Employee");
FindIterable<Document> cursor = coll.find((Bson) dbObj).projection((Bson) projectdbObj);
cursor.forEach(new Block<Document>() {
#Override
public void apply(final Document document) {
System.out.print(document);
}
});
}
Please help to optimize the code.
You can use Filters builder to build 'where' part and Projections builder to build 'select' part in MongoDB 3.0 without create object separately. Please refer below eg:
FindIterable<Document> cursor = coll.find(Filters.eq("employee.empid",1000)).projection(Projections.fields(Projections.include("emp_name"),Projections.excludeId());
Related
I am trying to do an easy search on a table that can be on any kind of database. The following query is working an the most databases, but I cannot find a solution which works on mysql.
The tables in my database are generated by the active objects framework, so I cannot change the names or config of those instances.
Here is the query that works fine on all databases but MySQL:
select * from "AO_69D057_FILTER" where "SHARED" = true AND "CONTAINS_PROJECT" = true AND UPPER("FILTER_NAME") like UPPER('%pr%').
MySql is not able to use the table name in double quotes for some reason. If I use the unquoted table name it works on MySQL but not on Postgres. Postgres is converting the table name to lowercase because it is unquoted. AO is generating the table names in upper case.
I also tried to use an alias, but that can not work because of the evaluation hierarchy of the statement.
Any suggestions how to get rid of the table name problem?
By default double quotes are used to columns.
You can change it:
SET SQL_MODE=ANSI_QUOTES;
Here is the documentation about it:
http://dev.mysql.com/doc/refman/5.7/en/sql-mode.html
I had the same problem. I select the query according to the exception I get. In the first call of the db search, I try without quotes if it fails then I try with quotes. Then I set useQueryWithQuotes variable accordingly so that in future calls I do not need to check the exception. Below is the code snipped I am using.
private Boolean useQueryWithQuotes=null;
private final String queryWithQuotes = "\"OWNER\"=? or \"PRIVATE\"=?";
private final String queryWithoutQuotes = "OWNER=? or PRIVATE=?";
public Response getReports() {
List<ReportEntity> reports = null;
if(useQueryWithQuotes==null){
synchronized(this){
try {
reports = new ArrayList<ReportEntity>( Arrays.asList(ao.find(ReportEntity.class, Query.select().where(queryWithoutQuotes, getUserKey(), false))) );
useQueryWithQuotes = false;
} catch (net.java.ao.ActiveObjectsException e) {
log("exception:" + e);
log("trying query with quotes");
reports = new ArrayList<ReportEntity>( Arrays.asList(ao.find(ReportEntity.class, queryWithQuotes, getUserKey(), false)));
useQueryWithQuotes = true;
}
}
}else{
String query = useQueryWithQuotes ? queryWithQuotes : queryWithoutQuotes;
reports = new ArrayList<ReportEntity>( Arrays.asList(ao.find(ReportEntity.class, query, getUserKey(), false)));
}
...
}
Hi i have this managed bean where it makes MySQL queries, the problem here is the SQL statement makes a '=' condition instead of 'LIKE'
Here is the code in my managed bean.
Connection con = ds.getConnection();
try{
if (con == null) {
throw new SQLException("Can't get database connection");
}
}
finally {
PreparedStatement ps = con.prepareStatement(
"SELECT * FROM Clients WHERE Machine LIKE '53'");
//get customer data from database
ResultSet result = ps.executeQuery();
con.close();
List list;
list = new ArrayList();
while (result.next()) {
Customer cust = new Customer();
cust.setMachine(result.getLong("Machine"));
cust.setCompany(result.getString("Company"));
cust.setContact(result.getString("Contact"));
cust.setPhone(result.getLong("Phone"));
cust.setEmail(result.getString("Email"));
//store all data into a List
list.add(cust);
}
return list;
Here the SELECT command does not pull all the numbers in 'Machine' column which is like 53, but if i enter a whole value, such as the complete number (53544) in place of 53 then the result is pulled up. I am confused !!
Also if i replace the above select statement with SELECT * FROM Clients the entire database is stored in list. Any ideas ?
Use wildcards:
Like '%53%'
...means everything that contains '53'.
Like '%53' - it ends with 53
LIKE '53%' - it starts with 53
You can also use _ if You want to replace a single character.
You can find a descriptipn HERE
You sql query should be
"SELECT * FROM Clients WHERE Machine LIKE '%53%'
I am trying to use system.dynamic.linq to create dynamic sorting.
this, is the query that I use:
var query = dalSession.Query<T>().AsQueryable();
var res = (from x in query orderby "x.FirstName" select x)
this is the mysql output:
select
affiliate0_.id as id0_,
affiliate0_.first_name as first6_0_,
from affiliate affiliate0_ order by 'x.FirstName' //FirstName as well
So you can see that the output went to the mysql query is the direct string, and not its reflection, ('x.FirstName') or ('FirstName').
This has no meaning in mysql context, it looks like I need order by affiliate0_.first_name.
Is there anyway to provide the Nhibernate the member itself? So the compiled query will be done normally?
You have to remove the " from you requiry. "x.FirstName" is seen as a string and translated to a sql string.
The "x" has no meaning inside the dynamic string.
Remove the x. (i.e. leave just "FirstName") and it should work.
Using a method call instead of the query comprehension syntax, you'd get:
var res = query.Orderby("FirstName")
Did you try it as follows (as Diego suggested)?
(from x in query select x).OrderBy("FirstName")
Because I think the dynamic linq orderby extension method is not executed when you use (x => "FirstName")
Otherwise try this:
(from x in query select x).OrderBy("it.FirstName")
BTW I renamed the OrderBy method in Dynamic.cs to DynamicOrderBy because I had some situations where the not dynamic linq OrderBy method was executed too:
public static IQueryable<T> DynamicOrderBy<T>(this IQueryable<T> source, string ordering, params object[] values) and use that one instead:
(from x in query select x).DynamicOrderBy("FirstName")
var param = Expression.Parameter("x");
var prop = Expression.Property(param, "FirstName");
var lambda = Expression.Lambda<Func<User, string>>(prop, param);
query.Orderby(lambda);
i want to be able to do such a projection:
var result = from record in MyTable
select MapTo( record );
/*
select new RecordModel( )
{
RecordId = record.Id,
Property1 = record.Property1
};
*/
private RecordModel MapTo( MyTable dbRecord )
{
return new RecordModel( )
{
RecordId = dbRecord.Id,
Property1 = dbRecord.Property1
};
}
but i always get a 'NotSupportedException' (has no supported translation to sql).
I'm not sure if this is even possible but it would be nice^^
Maybe this is possible when i use an expression but i don't know how to code such an expression.
Linq tries to add the method to the query and sees it cannot be translated to Sql.
To be able to execute any CLR method in the Linq query, you need to execute the sql part of it first, so that you operate on in-memory objects. Like this:
var result = from record in MyTable.ToList()
select MapTo(record);
Anything that forces MyTable to enumerate its entries should work.
I have problem when I try to display data(the result of a query) from my database mysql to my jTextarea, when I compile I have an error exception like:
SQL Exception: java.sql.SQLException: Can not issue SELECT via executeUpdate()
I have used a "select" query from my table where the name is the name written in my jTextFieldNom,this is my code, I hope that some one help me because I don't know how to resolve the problem, I 'm sure that my query is correct but I don't know where is the problem.
String pilote = "com.mysql.jdbc.Driver";
jComboBoxType.addItemListener(new ItemState());
jComboBoxMenaces.addItemListener(new ItemState());
try {
Class.forName(pilote);
Connection connexion = DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root"," ");
Statement instruction = connexion.createStatement();
String a=jTextFieldNom.getText();
String SQL = "select description from table where nomcol="+a+";";
ResultSet rs = instruction.executeQuery(SQL);
instruction = connexion.createStatement();
int rowsEffected = instruction.executeUpdate(SQL);
jTextArea1.append(rs.getString("description"));
}
...... //bloc catch
This line is executing a Select statement which is throwing the error.
int rowsEffected = instruction.executeUpdate(SQL);
You don't need this line because you aren't updating your database.
Also change the append to setText
jTextArea1.setText(rs.getString("description"));
Try this:
String pilote = "com.mysql.jdbc.Driver";
jComboBoxType.addItemListener(new ItemState());
jComboBoxMenaces.addItemListener(new ItemState());
try {
Class.forName(pilote);
Connection connexion = DriverManager.getConnection(
"jdbc:mysql://localhost:3306/test","root"," ");
Statement instruction = connexion.createStatement();
String a=jTextFieldNom.getText();
String SQL = "select description from table where nomcol="+a+";";
ResultSet rs = instruction.executeQuery(SQL);
jTextArea1.setText(rs.getString("description"));
}