in my db,i have 4 tables employee,customer,product & orders.
i m trying linq to sql and wrote the following expression:
NorthwindDataContext db = new NorthwindDataContext();
var matchingEmployees = from employee in db.Employees
where employee.emp_city = "pune"
select employee;
but it reflects following error:
Error 1 Cannot implicitly convert type 'string' to 'bool'
i have given emp_city as nvarchar(50)
how to resolve the problem
NorthwindDataContext db = new NorthwindDataContext();
var matchingEmployees = from employee in db.Employees
where employee.emp_city == "pune" // == not =
select employee;
Related
I am very new to writing LINQ statements, and I am struggling to write this simple SQL in LINQ form.
SELECT Type, COUNT(*) as [Total Submissions]
FROM Submission
GROUP BY Type
this is my attempt:
var query = from s in db.Submission
group s.Type
Type = s.Type
Total = s.Type.Count()
This is what my output should be:
Type Count of Type
Book 10
Chapter 15
Journal 8
Conference 4
Using LINQ syntax:
var result = from x in db.Submission
group x by x.Type into grp
select new {
Type = grp.Key,
Count = grp.Count()
};
Using lambda syntax:
var result = db.Submission
.GroupBy(x => x.Type)
.Select(x => new {
Type = x.Key,
Count = x.Count()
});
I am new to CakePhp and want to Update record.
I have successfully fetched records from my table.
$SQL = "SELECT Id, Name FROM Table WHERE Id = '123';
return Hash::combine($this->query($SQL), '{n}.{n}.Id', '{n}.{n}');
Above code returns records properly.
Table Name: Table__c
Model Name: Table.php
Controller Name: TablesController.php
I have tried following:
$sObjects = array();
$sObject = new stdClass();
$sObject->Id = 123;
$sObject->Name = "abc";
array_push($sObjects, $sObject);
$result = $this->Table__c->save($sObjects);
which gives me error: Call to a member function save() on a non-object
Earlier I was using Salesforce and following code was fine:
$this->query(array('update', $sObjects, 'Table__c'));
But with MySQL it gives me error:
SQLSTATE[42000]: Syntax error or access violation: 1065 Query was empty
Thank you guys for your comments I appreciate that.
Answer:
If your table name and model name do not match by adding in your model class:
var $useTable = 'Table_Name';
you can use that table.
Now how are you going to update record in this table:
$sObject = new stdClass();
$sObject->Name = "'abc'";
$sObject->Address = "'xyz'";
$condition = array('Id' => "123");
$this->updateAll((array)$sObject, $condition);
updateAll() function will update records matching the $condition
I'm using LINQ to SQL to select records. I need to union two queries together but the select statements are being changed so that the expressions no longer match preventing the union.
This LINQ query omits my forced columns 'resultType' and 'imageFile' from the final result.
var taglist = from t in dc.ProductTags
where t.Tag.StartsWith(prefixText)
select new AutoSearch {
resultType = "Tag",
name = t.Tag,
imageFile = string.Empty,
urlElement = t.Tag };
This is the query that is presented.
{SELECT [t0].[Tag] AS [name] FROM [dbo].[ProductTag] AS [t0] WHERE [t0].[Tag] LIKE #p0}
This is the second query to be unioned with the initial one.
var brandlist = from b in dc.Businesses
join t in dc.Tags on b.BusinessId equals t.BusinessId
where b.Name.StartsWith(prefixText)
where b.IsActive == true
where t.IsActive == true
select new AutoSearch
{
resultType = "Business",
name = b.Name,
imageFile = t.AdImage,
urlElement = b.BusinessId.ToString() };
This is the sql for the second query.
SELECT [t0].[Name] AS [name], [t1].[AdImage] AS [imageFile], CONVERT(NVarChar(MAX) [t0].[BusinessId]) AS [urlElement] FROM [dbo].[Business] AS [t0] INNER JOIN [dbo].[Tag] AS [t1] ON ([t0].[BusinessId]) = [t1].[BusinessId] WHERE ([t0].[Name] LIKE #p0)
The union... that throws the error.
var unionedResults = taglist.Union(brandlist);
The error thrown.
All queries combined using a UNION, INTERSECT or EXCEPT operator must have an equal number of expressions in their target lists.
This is the AutoSearch class.
public class AutoSearch
{
public string name { get; set; }
public string imageFile { get; set; }
public string resultType { get; set; }
public string urlElement { get; set; }
}
Suggestions as to what is going???
UPDATE***
Found a work around...
Found the issue.
This is a known bug in LINQ, several discussions found here on SO that pointed me in the right direction. Turns out most of the work arounds listed on the site are no longer valid because version 4.0 of broke them too. I found another that worked..
LINQ omits duplicate values for optimization purposes. I was able to change the values of the throw away fields by converting them to strings or lower case or concatenating them.
Terribly inefficient, but it works. Whole day lost for me on this one, perhaps it will save others time.
var taglist = from t in dc.ProductTags
where t.Tag.StartsWith(prefixText)
let resultType = "Tag"
select new AutoSearch() {
resultType = resultType,
name = t.Tag,
imageFile = t.Tag.ToString(),
urlElement = t.Tag.ToLower()
};
var brandlist = from b in dc.Businesses
join t in dc.Tags on b.BusinessId equals t.BusinessId
where b.Name.StartsWith(prefixText)
where b.IsActive == true
where t.IsActive == true
where t.AdImage != null
where t.AdImage != String.Empty
let resultType = "Business"
select new AutoSearch
{
resultType = resultType,
name = b.Name,
imageFile = t.AdImage,
urlElement = b.BusinessId.ToString()
};
The only property you reference when you do the select part of your query is Tag, Linq to Sql knows this and optimizes the query to only select columns you're referencing.
In other words, this section of your query only refers to the "Tag" property, which is tied to the Tag column on your database.
new AutoSearch {
resultType = "Tag",
name = t.Tag,
imageFile = string.Empty,
urlElement = t.Tag };
What Linq does in this case is pass an expression to the underlying provider (very similar to a binary tree data structure). The provider then parses this tree and creates a SQL query from it at run time. The optimization is done by the provider at runtime which results in the SQL query you're seeing.
Update
For the second problem with the union you basically are trying to union two different SQL statements which is causing the union error. So lets take a look.
The resulting statement that would be causing the error would look something like this
SELECT [t0].[Tag] AS [name] FROM [dbo].[ProductTag] AS [t0] WHERE [t0].[Tag] LIKE #p0
UNION
SELECT [t0].[Name] AS [name], [t1].[AdImage] AS [imageFile], CONVERT(NVarChar(MAX) [t0].[BusinessId]) AS [urlElement] FROM [dbo].[Business] AS [t0] INNER JOIN [dbo].[Tag] AS [t1] ON ([t0].[BusinessId]) = [t1].[BusinessId] WHERE ([t0].[Name] LIKE #p0)
Obviously this is problametic since there is not the same number of columns between the two and that doesn't fly with SQL. While I do not have a pure linq solution there is a workaround.
First You'll need to create a SQL function that just returns a string sent to it.
CREATE FUNCTION ReturnString( #string varchar(max) )
RETURNS varchar(max)
AS
BEGIN
RETURN #string
END
GO
Next drag and drop this new SQL function into your dbml file, and finally in your query simply call the method where appropriate.
var taglist = from t in dc.ProductTags
where t.Tag.StartsWith(prefixText)
select new AutoSearch
{
resultType = dc.ReturnString("Tag"),
name = t.Tag,
imageFile = dc.ReturnString(string.Empty),
urlElement = dc.ReturnString(t.Tag)
};
var brandlist = from b in dc.Businesses
join t in dc.Tags on b.BusinessId equals t.BusinessId
where b.Name.StartsWith(prefixText)
where b.IsActive == true
where t.IsActive == true
select new AutoSearch
{
resultType = dc.ReturnString("Business"),
name = b.Name,
imageFile = t.AdImage,
urlElement = b.BusinessId.ToString()
};
Now you should be able to perform the union.
How can I get linq pad to run my left join as show below?
var query =
from s in db.CDBLogsHeaders
.OrderByDescending(g => g.LogDateTime)
from sc in db.StyleColors
.Where(stylecolor => stylecolor.id == (int?)s.StyleColorID)
.DefaultIfEmpty()
from c in db.StyleHeaders
.Where(styleHeader => styleHeader.id == (int?)s.StyleHeaderID)
.DefaultIfEmpty()
select new
{
CDBLogsHeaderId = s.Id,
Merchandiser = c.Merchandiser,
Material = s.Material,
Season = s.Season,
LogsHeaderLogType = s.LogType,
PushFromTo = s.PushFromTo,
LinePlan = s.LinePlan,
QuikRefNumber = s.QuikRefNumber,
PLMOrigin = s.PLM_Origin,
SeasonOriginal = c.SeasonOriginal,
SeasonCurrent = c.SeasonCurrent,
StyleHeaderId = c.Id,
StyleCode = c.StyleCode,
StyleColorsColorCode = sc.ColorCode
};
query.Dump();
The sql that linq pad creates runs perfectly in Management Studio but linq-pad doesn't display any rows and gives this error
InvalidOperationException: The null value cannot be assigned to a
member with type System.Int32 which is a non-nullable value type.
How can I get linqpad to work so I can play with it?
In your anonymous type, make sure your ints are returning ints.
Change
StyleHeaderId = c.Id,
To
StyleHeaderId = (c.Id == null ? 0 : c.Id),
I have SQL database as follows
alt text http://img97.imageshack.us/img97/5774/dbimage.jpg
Now I want to filter the restaurant_detail table for the parameters:
1. cuisine 2. area
Can you help me to build LINQ query?
I presume you have a model generated either with LINQ to SQL or Entity Framework. Also, I'm assuming foreign key relationships have been set.
var details = db
.Cuisines
.Where(c => c.Cuisine=="something")
.SelectMany(c => c.RestaurantCuisines)
.Select(rc => rc.Restaurant.RestaurantDetails)
.Where(rd => rd.Area=="something")
;
Done with the linq query using following lines of code :
c = from q in dc.restaurant_cuisines
where q.cuisine.cuisine1.Contains(cuisine)
&& q.restaurant.price.ToString().Length == price.Length
select new NearBy { NearById = q.restaurant.id, NearByLongitude = (double)q.restaurant.longitude, NearByLatitude = (double)q.restaurant.latitude };
}
int[] ids = new int[c.Count()];
var lon = from q1 in dc.area_maps where q1.area.ToLower() == area.ToLower() select q1.longtitude;
var lat = from q1 in dc.area_maps where q1.area.ToLower() == area.ToLower() select q1.latitude;
foreach(NearBy n in c)
{
result = calcDistNew((double)lat.FirstOrDefault(), (double)lon.FirstOrDefault(), n.NearByLatitude, n.NearByLongitude);
ids[i++] = n.NearById;
}
var r = from q in dc.restaurant_details
where 1 == 1 &&
(ids).Contains(q.restaurant_id)
select new Restaurant
{
Restora_id = q.restaurant_id.ToString(),
Name = q.restaurant.name,
Foodtype = q.restaurant.foodtype.foodtype1,
Avg_rating = q.restaurant.avg_rating.ToString(),
Featured = q.restaurant.featured.ToString(),
CuisineList = getCuisine(q.restaurant_id),
Restora_type = q.type,
Distance = Math.Round(calcDistNew((double)lat.FirstOrDefault(), (double)lon.FirstOrDefault(), (double)q.restaurant.latitude, (double)q.restaurant.longitude), 2),
Newarrival = q.restaurant.newarrival.ToString(),
CountRecord = ids.Length.ToString()
};
var d = r.AsEnumerable().OrderBy(t => t.Distance);
var g = d.Take(recordSize + 10).Skip(recordSize);
return g.ToList();
Please note that above displayed code generated with some changes from the initial requirements.