I'm looking for a way to get special fields from mongoskin find function. in other words in SQL lang we say select column1,column2,column3 from mytable rather than select *
currently my query is like below and i want to get specify the fields that I'm looking for rather the the whole json object.
db.collection('collacta').find().toArray(function(err, result) {
if (result) {
...
} else {
...
};
});
thanks
For getting the projection of fields, you should pass the DBObject for projection,
DBCursor cursor = collection.find(query, projectionQuery);
The projection is The DBObject in form of key-value pair. where,
key is the name of field you want to project. value can be either 0 or 1.
0 - means exclude the particular column from result set.
1 - means include the particular column in result set.
For more info, see here.
Related
This seems like it would be straightforward to do but I just can not figure it out. I have a query that returns an ARRAY of strings in one of the columns. I want that array to only contain unique strings. Here is my query:
SELECT
f."_id",
ARRAY[public.getdomain(f."linkUrl"), public.getdomain(f."sourceUrl")] AS file_domains,
public.getuniqdomains(s."originUrls", s."testUrls") AS source_domains
FROM
files f
LEFT JOIN
sources s
ON
s."_id" = f."sourceId"
Here's an example of a row from my return table
_id
file_domains
source_domains
2574873
{cityofmontclair.org,cityofmontclair.org}
{cityofmontclair.org}
I need file_domains to only contain unique values, IE a 'set' instead of a 'list'. Like this:
_id
file_domains
source_domains
2574873
{cityofmontclair.org}
{cityofmontclair.org}
Use a CASE expression:
CASE WHEN public.getdomain(f."linkUrl") = public.getdomain(f."sourceUrl")
THEN ARRAY[public.getdomain(f."linkUrl")]
ELSE ARRAY[public.getdomain(f."linkUrl"), public.getdomain(f."sourceUrl")]
END
I am using MongoDB with hapi.JS. I have a collection which contains few rows in the schema. I want to sort the rows in either asc order or desc order but want to mention it in the URI. for example the URI should look something like this
/api/v1/customers?sort=name&direction=asc&limit=30
How can I sort this collection by asc or desc order and limit can be fixed or flexible as well.
I have defined like this as of now but even if I mention the sort in URI it gives the output only in asc order.
Models.Account.find(criteria,projection,{skip:5,limit:5},function(err,resp){
if(err)
callbackRoute(err);
else
callbackRoute(err,resp);
}).sort({[_id]:"asc"});
db.yourcollection.find(...).sort({ name:1 }).limit(30)
or with dynamic values:
// following is ECMA 6 only
// get params and make sure values are what you expect (check for injection) + direction must be = "asc" || "desc"
db.yourcollection.find(...).sort({ [sort]: direction }).limit(30)
I have field Value in table finStatementTrans which is array.
How should I write select syntax with group by and sum by this field?
while select finStatementTable join DataClassParagraph,sum(Value) from finStatementTrans
group by finStatementTrans.DataClassParagraph
where finStatementTable.RecId == finStatementTrans.FinStatementTable_FK
&& finStatementTable.FinStatementTableParent_FK == 5637569094
{
info(strFmt(%1,%2",finStatementTrans.DataClassParagraph,finStatementTrans.Value[1]));
}
Is this correct?
sum(Value[1])
with this I can't compile.
As Aliaksandr Maksimau mentioned in his comment, aggregating array fields is not possible. Aggregations are only supported for integer and real data type fields.
See also X++ data selection and manipulation, paragraph select statements, last sentence.
I am currently getting a list of related field like so
List ( join_table::id_b;)'
and what i would like to do is filter that list by a second field in the same related table pseudo code as follows
List ( join_table::id_b;jointable:other="foo")
not really sure how to filter it down
The List() function will return a list of (non-empty) values from all related records.
To get a list filtered by a second field, you could do any one of the following:
Define a calculation field in the join table = If ( other = "foo" ; id_b ) and use this field in your List() function call instead of the id_b field;
Construct a relationship filtered by the other field;
Use the ExecuteSQL() function instead of List();
Write your own recursive custom function (requires the Advanced version to install).
I am using mongo's shell and want to do what is basically equivalent to "SQL's select col INTO var" and then use the value of var to look up other rows in the same table or others (Joins). For example, in PL/SQL I will declare a variable called V_Dno. I also have a table called Emp(EID, Name, Sal, Dno). I can access the value of Dno for employee 100 as, "Select Dno into V_Dno from Emp where EID = 100). In MongoDB, when I find the needed employee (using its _id), I end up with a document and not a value (a field). In a sense, I get equivalent to the entire row in SQL and not just a column. I am doing the following to find the given emp:
VAR V_Dno = db.emp.find ({Eid : 100}, {Dno : 1});
The reason I want to do this to traverse from one document into the other using the value of a field. I know I can do it using the DBRef, but I wanted to see if I could tie documents together using this method.
Can someone please shed some light on this?
Thanks.
find returns a cursor that lets you iterate over the matching documents. In this case you'd want to use findOne instead as it directly returns the first matching doc, and then use dot notation to access the single field.
var V_Dno = db.emp.findOne({Eid : 100}, {Dno : 1}).Dno;
Using your query as a starting point:
var vdno = db.emp.findOne({Eid: 100, Dno :1})
This returns a document from the emp collection where the Eid = 100 and the Dno = 1. Now that I have this document in the vdno variable I can "join" it to another collection. Lets say you have a Department collection, a document in the department collection has a manual reference to the _id field in the emp collection. You can use the following to filter results from the department collection based on the value in your variable.
db.department.find({"employee._id":vdno._id})