Given 2 base tables, 1 table which stores the relation between them with a few extra attributes; taking a few extra attribute values as user input, based on that extracting relation from relation table.
This information has the ID of the main values (person and animal) not the names. I want to display the names on screen, like according to the input you gave the records which found are this person has this animal with him.
select DISTINCT table0.person_name, table5.animal_name
from table1
INNER JOIN table0, table5
on table1.person_id=table0.person_id
and
table1.animal_id=table5.animal_id
where table1.aa=input1
and table1.bb=input2
and table1.cc=input3
and table1.dd=input4
You have at least three errors.
The WHERE clause should come after the JOIN .. ON clause, not before it.
You cannot refer to columns in table5 because it doesn't appear in the FROM list.
You shouldn't write ON xxx AND ON yyy. Just write ON xxx AND yyy.
Other points to consider:
Are you sure that you meant FULL OUTER JOIN and not INNER JOIN?
Why do you add the distinct? If a person owns two animals with the same name do you really want to return only one row?
Where do the values input1, ..., input4 come from?
I think table0 should be renamed to person, table5 to animal, and table1 to person_animal to make it easier to understand the purpose of each table.
My best guess as to what you meant is this:
SELECT table0.person_name, table5.animal_name
FROM table1
JOIN table0 ON table1.person_id = table0.person_id
JOIN table5 ON table1.animal_id = table5.animal_id
WHERE table1.aa = input1
AND table1.bb = input2
AND table1.cc = input3
AND table1.dd = input4
Related
There may be similar questions out here but none that I could find for doing a subSelect in the FROM clause as a virtual table.
Most of the columns I need are in one table. There are a few columns needed from different tables that I cannot join on without getting a Cartesian join.
Here is my SQL query:
SELECT meter_name, a.loc_id, a.loc_name, a.facility_name, meter_type
FROM meter_table, (SELECT loc_id, loc_name, facility_name
FROM facility_table
WHERE id = 101) a
WHERE meter_id = a.fac_id
I have no idea how to convert this into Linq and it must be done tonight for a demo in the morning.
Assume this represents your meter_table within your database
in this case each element of the list represents a record in the database table holding the appropriate attributes
i.e the table columns will become the properties of each object
List<Meter> meter_table = new List<Meter>();
Assume this represents the facility_table table you want to join with.
same goes here, each element of the list represents a record in the database table holding the appropriate attributes
i.e the table columns will become the properties of each object
List<Facility> facility_table = new List<Facility>();
then perform the inner join like so:
var query = from m in meter_table
join a in facility_table on m.meter_id equals a.fac_id
where a.id == 101
select new { meter_name = m.MeterName,
loc_id = a.LocId,
facility_name = a.FacilityName,
meter_type = m.MeterType
};
where m.MeterName, a.LocId, a.FacilityName, m.MeterType are properties of their respective types.
it's also worth noting the variable query references an IEnumerable of anonymous types. However, if you want to return an IEnumerable of strongly typed objects then feel free to define your own type with the appropriate properties then just change select new to:
select new typeName { /* assign values appropriately */}
of the above query.
Table A has - ID(PK), PartNumber, Code1, Code2
Table B has - InventoryID(PK) PartNumber, Part, and a bunch of other columns.
I need to get everything from Table B where Table B's PartNumber is NOT in Table A.
Example: Table B has PartNumber 123. There is no PartNumber in Table A for 123. Get that row.
What I currently have:
using (SomeEntity context = new SomeEntity())
{
var partmasterids = context.PartsMasters.Select(x => x.PartNumber).Distinct().ToList();
var test = context.Parts.Where(x => !partmasterids.Contains(x.PartNumber)).ToList();
}
I currently first get and select all the distinct part numbers from Table A.
Then I check Table A and Table B's partnumbers and get each part from Table B where there that part number is not in Table A.
There are about 11,000 records in table B and 200,000 records in table A.
I should be getting about 9000 parts which are not in table A.
I am running into huge performance issues with that second LINQ statement. If I do a .Take(100), that will even take around 20-30 seconds. Anything above 1000 will take way too long.
Is there a better way to write this LINQ statement?
From what I understand of your question, the equivalent in SQL would be something like
SELECT DISTINCT B.PartNumber AS MissingParts
FROM TableB as B
LEFT OUTER JOIN TableA as A ON B.PartNumber = A.PartNumber
WHERE A.PartNumber IS NULL
Run that SQL and measure the time it takes. Without indexes, that's as fast as it's going to get.
Now, if you really have to do it in EF, you'll need to do an equivalent statement, complete with the left join. Based on this question, it would look something like this
var query = from b in TableB
join a in TableA on b.PartNumber equals a.PartNumber into joind
from existsInA in joind.DefaultIfEmpty()
where existsInA == null
select b.PartNumber;
var missingParts = query.Distinct().ToList();
I'm trying to get a list of servers thay may or may not belong to 1 or more groups to display in a grid.
Example
ServerID IP GroupID
1 192.168.1.44 1
1 192.168.1.44 10
2 192.168.1.45 1
3 192.168.1.46 2
4 192.168.1.47 null
5 192.168.1.48 null
If I have no records In the GroupServer Table. (Since there is no groups or groups exist but they are not assigned) I expect to get something like this:
ServerID IP GroupID
1 192.168.1.44 null
2 192.168.1.45 null
3 192.168.1.46 null
4 192.168.1.47 null
5 192.168.1.48 null
Since is a Many-to-Many relationship. I have
Group Table
Server Table
GroupServer Table
I could not find a LINQ Pivot Table example.
So I tried to buid my own.
var query = (from sg in context.ServerGroups
join servers in context.Servers on sg.ServerID equals servers.ID
join groups in context.Groups on sg.GroupID equals groups.ID
into serverxgroup
from gAddrBilling in serverxgroup.DefaultIfEmpty()
select new
{
ServerID = sg.ServerID,
ServerIP = server.IP,
GroupID = sg.GroupID
});
The Query above does not retrieve anything
And I quiet dont understand what the "from gAddrBilling" is for. Since I modify a snippet I was trying to make work. So I wonder if someone has already faced a problem like this and give me some hint, snippet or advice about what is what I'm missing.
Thank you.
First, this is not a pivot query, but a regular query on many-to-may relationship via explicit junction table.
Second, looks like you are using Entity Framework, in which case you'd better define and use navigation properties rather than manual joins.
Third, and the most important, the structure of the query is wrong. If you want to get a list of servers that may or may not belong to 1 or more groups, then you should start your query from Servers (the table which records you want to be always included, not from link table where some ServerID are missing) and then use left outer joins to the other tables like this:
var query =
from s in servers in context.Servers
join sg in context.ServerGroups on s.ID equals sg.ServerID
into s_sg from sg in s_sg.DefaultIfEmpty() // make the above LEFT OUTER JOIN
// You can remove the next two lines if all you need is the GroupId
// and keep them if you need some other Group field in the select
join g in context.Groups on sg.GroupID equals g.ID
into sg_g from g in sg_g.DefaultIfEmpty() // make the above LEFT OUTER JOIN
select new
{
ServerID = s.ID,
ServerIP = s.IP, // or sg.IP?
GroupID = (int?)sg.GroupID
};
I have a list of SiteUsers in one table and another table has columns with different types of owners (ID) for the record. For example, the SiteUserID in the SiteUsers table will be used for the SalesRepID, the StaffingManagerID, and RecruiterID in the Fill table. Of course, the SiteUserID is different for each of the values in the Fill table.
I'd like to return the name of the SiteUser for each ID column in the Fill Table.
How do I properly construct a JOIN statement to do this?
I'm guessing this is done through INNER JOIN, but I'm not sure.
My current select statement already has an INNER JOIN as I'm pulling the name of the FillType from another table. I'm using this in an asp.net application.
I'm not sure if this is even possible. Any help is appreciated.
Since each of the IDs in the Fills table allows null, you probably want to LEFT JOIN to the SiteUsers table like so:
SELECT f.FillID, s1.SiteUserLastName 'SalesRep', s2.SiteUserLastName 'StaffingManager', s3.SiteUserLastName 'Recruiter'
FROM Fills f
LEFT JOIN SiteUsers s1 on f.SalesRepID = s1.SiteUserID
LEFT JOIN SiteUsers s2 on f.StaffingManagerID = s2.SiteUserID
LEFT JOIN SiteUsers s3 on f.RecruiterID = s3.SiteUserID
You can always UNPIVOT the results like so:
SELECT
DISTINCT
unpvt.FillID
,unpvt.RepID
,unpvt.RepType
,s.SiteUserFirstName
,s.SiteUserLastName
FROM
(SELECT
FillID
,SalesRepID
,StaffingManagerID
,RecruiterID
FROM Fills
) f
UNPIVOT
(RepID FOR RepType IN
(SalesRepID, StaffingManagerID,RecruiterID)
) AS unpvt
JOIN SiteUsers AS s on unpvt.RepID = s.SiteUserID`
Obviously you can play with exact output (such as substituting the RepType for a different value with a CASE statement or whatnot.
My question is: why the piss-poor design? Instead of having three IDs in the Fills table, you should have a junction table between SiteUsers and Fills to allow many-to-many relationships. IF it were designed with a junction table, you'd never have had to ask this question.
You will have to join the Fill table with the SiteUsers table multiple times, one for each xxxID column in the Fills for which you want the SiteUser name and combine the results using an union as below:
select a.SiteUserId, a.SiteUserFirstName, a.SiteUserLastName
from dbo.SiteUsers a
inner join dbo.Fills b on b.SalesRepId = a.SiteUserId
UNION
select a.SiteUserId, a.SiteUserFirstName, a.SiteUserLastName
from dbo.SiteUsers a
inner join dbo.Fills b on b.StaffingManagerId = a.SiteUserId
UNION
select a.SiteUserId, a.SiteUserFirstName, a.SiteUserLastName
from dbo.SiteUsers a
inner join dbo.Fills b on b.RecruiterId = a.SiteUserId
I am not sure if this can be done, but here's the scenario.
I want to turn this sql into linq:
SELECT * FROM Department d
INNER JOIN Employee e ON e.DepartmentID = d.DepartmentID
Department - Employee is 1 to many relationship.
I have created a custom object that I would like to populate the result into.
public class DepartmentSummary
{
public Department Department { get; set; }
public List<Employee> Employees {get; set;}
}
The Linq I came up with is
var result = from d in dba.Department
join e in dba.Employee d.DepartmentID equals e.DepartmentID into j1
select new DepartmentSummary
{
Department = d,
Employees = j1.ToList()
};
I tried it out and it's not working. Can anyone shed some light for me please? I would like to perform an inner join between Department and Employee. For each Department in the resultset, I would like to create one DepartmentSummary object which holds that department and a list of employees belonging to that department.
Does Linq provides an ad hoc solution for this or must I iterates through the result set and create a list of DepartmentSummary manually?
Thanks,
EDIT:
Looks like this works for me
var result = from d in dba.Department
join e in dba.Employee d.DepartmentID equals e.DepartmentID into j1
where j1.Count() > 0
select new DepartmentSummary
{
Department = d,
Employees = j1.ToList()
};
The thing is that you're not really taking one SQL and trying to create a Linq-query out of it.
If you were, you'd notice that your SQL query does not really produce one row per department, but it will repeat the department information for each employee in that department.
Now, an initial naive look would suggest you use a group-by clause, since that would allow you to split the data into individual groupings for each department, but groupings in SQL does not really give you a key+all-matching-rows type of result, rather it allows you to do aggregate calculations, like "for each department, how many employees do I have".
So, in order to do what you want, you need to basically do a normal join, which will give you each employee, coupled with the appropriate department information (ie. each employee will be linked to his/her department), and then you need to construct the rest of the data structure yourself.
Now, having said that, if you have the proper relationships set in your data context related classes, each department should already have some kind of property that contains all employees in that department, so perhaps the simple query is just "give me all departments", and then you can, for each department, retrieve the employees?
Of course, doing that would likely execute one SQL for each department, but in this case, you're back to "give me all employees with their department information" and you have to build code to handle the rest.
LINQ to SQL doesn't understand your ToList() call, but you might be able to select the sequence of joined elements and then use LINQ to Objects (via AsEnumerable()) to map to your DepartmentSummary object:
var qResult = from d in dba.Department
join e in dba.Employee d.DepartmentID equals e.DepartmentID into j1
select new
{
Department = d,
Employees = j1
};
var result = from d in qResult.AsEnumerable()
select new DepartmentSummary()
{
Department = d.Department,
Employees = e.Employees.ToList()
};
Sounds like you're looking to get around lazy loading?
DataLoadOptions dlo = new DataLoadOptions();
dlo.LoadWith<Department>(d => d.Employees);
using (var dba = new MyDataContext())
{
dba.LoadOptions = dlo;
var result = from d in dba.Department
select d;
}
Now, if you don't have a relationship defined between Department and Employees (the Linq2Sql designer will do this for you if you have database relationships setup) then you should look into doing that. It makes it all dramatically easier. In fact, you don't even need your campaign summary.
This problem is due to the nature of the query. When you join Department to Employee, you'll get back one record for every Employee. This means that your ToList() statement is expecting multiple employees per department, but due to the join, always getting one.
Change your query to
var result =
from d in dba.Department
select new tCampaignSummary
{
Department = d,
Employees = dba.Employee.Where(e => e.DepartmentID ==
d.DepartmentID).ToList()
};
I've tested this and it works.
What it does differently is selects only one record per Department (not per employee) then it gets the zero to many corresponding employees for each dept and converts them to a list.
Good luck!
EDIT
As requested, here is the generated SQL:
SELECT [t0].*, [t1].*
(
SELECT COUNT(*)
FROM [dbo].[Employee] AS [t2]
WHERE [t2].[DepartmentID] = [t0].[DepartmentID]
) AS [value]
FROM [dbo].[Department] AS [t0]
LEFT OUTER JOIN [dbo].[Employee] AS [t1]
ON [t1].[DepartmentID] = [t0].[DepartmentID]
ORDER BY [t0].[DepartmentID], [t1].[IndexID]
The only modification is that LINQ will not do [t0].*, instead it will enumerate each field. Since I had to guess at the fields, I left them out to make the SQL clearer.