I have the following query trying to get count of a query:
var testQuery = Db
.From<Blog>()
.LeftJoin<BlogToBlogCategory>()
.Where(x => x.IsDeleted == false)
.OrderBy(x => x.ConvertedPrice);
var testCount = Db.Scalar<int>(testQuery.Select<Blog>(x => Sql.CountDistinct(x.Id)));
var results = Db.LoadSelect(testQuery.SelectDistinct());
It gives error:
42803: column "blog.converted_price" must appear in the GROUP BY clause or be used in an aggregate function
Issue seems to be the orderby statement. If I remove it then the error goes away. Why does this stop count distinct working?
I am having to clear orderby on all queries I do like this. Is it supposed to work this way?
Also I just realised count is wrong. Results is 501 unique records and testCount is 538.
What am I doing wrong?
Whenever in doubt with what an OrmLite query is generating, you can use the BeforeExecFilter to inspect the DB command before its executed or to just output the query to the Console you can use:
OrmLiteUtils.PrintSql();
You shouldn't be using OrderBy with aggregate scalar functions like COUNT which is meaningless and will fail in your case because it needs to included the GROUP BY clause for joined table queries.
Your specifically querying for COUNT(DISTINCT Id) if you wanted the row count for the query you can instead use:
var testCount = Db.RowCount(testQuery);
If you wanted to use COUNT(*) instead, you can use:
var testCount = Db.Count(testQuery);
Related
In my AutoQuery request I have a left join specified so I can query on properties in the joined table.
public class ProductSearchRequest : QueryDb<Book>
, ILeftJoin<Book, BookAuthor>, ILeftJoin<BookAuthor, Author>
{}
If I use standard way of autoquery like so:
var q = AutoQuery.CreateQuery(request, base.Request);
var results = AutoQuery.Execute(request, q);
And 100 are being requested, then often less than 100 will be retuned as the Take() is based on results with a left join.
To remedy this I am doing this instead:
var q = AutoQuery.CreateQuery(request, base.Request);
q.OrderByExpression = null //throws error if orderby exists
var total = Db.Scalar<int>(q.Select(x => Sql.CountDistinct(x.Id))); //returns 0
var q1 = AutoQuery.CreateQuery(request, base.Request).GroupBy(x => x);
var results = Db.Select<Book>(q1);
return new QueryResponse<Book>
{
Offset = q1.Offset.GetValueOrDefault(0),
Total = total
Results = results
};
The group by appears to return correct number of results so paging works but the Total returns 0.
I also tried:
var total2 = (int)Db.Count(q1);
But even though q1 has a GroupBy() it returns the number of results including the left join and not the actual query
How can I get the true total of the query?
(Getting some official docs on how to do paging and totals with autoquery & left join would be very helpful as right now it's a bit confusing)
Your primary issue stems from trying to return a different total then the actual query AutoQuery executes. If you have multiple left joins, the total is the total results of the query it executes not the number of rows in your source table.
So you're not looking for the "True total", rather you're looking to execute a different query to get a different total than the query that's executed, but still deriving from the original query as its basis. First consider using normal INNER JOINS (IJoin<>) instead of LEFT JOINS so it only returns results for related rows in joined tables which the total will reflect accordingly.
Your total query that returns 0 is likely returning no results, so I'd look at looking at the query in an SQL Profiler so you can see the query that's executed. You can also enable logging of OrmLite queries with Debug logging enabled and in your AppHost:
OrmLiteUtils.PrintSql();
Also note that GroupBy() of the entire table is unusual, you would normally group by a single or multiple explicit selected columns, e.g:
.GroupBy(x => x.Id);
.GroupBy(x => new { x.Id, x.Name });
I'm trying to get a distinct result set of tuples, but the Distinct never gets added to query.
Example
List<Tuple<Alpha, Beta>> results;
var q = dbConn.From<Alpha>()
.Join<Alpha, Beta>((a, b) => a.Id == b.AlphaId)
...
... more joins and Wheres
...
.SelectDistinct();
results = dbConn.SelectMulti<Alpha, Beta>(q);
Adding the SelectDistinct, or not, make no difference to the outputted SQL and hence results.
How do I get SelectMulti to work with Distinct?
Thanks.
I've just added support for this in this commit where if .SelectDistinct() is used in the SqlExpression<T> then it will execute the SQL query using SELECT DISTINCT, e.g:
var results = dbConn.SelectMulti<Alpha, Beta>(q.SelectDistinct());
This change is available from v5.4.1 that's now available on MyGet.
Is it possible to use .QueryMultiple (or some other method) in Dapper, and use the results of each former query to be used in the where clause of the next query, without having to do each query individually, get the id, and then .Query again, get the id and so on.
For example,
string sqlString = #"select tableA_id from tableA where tableA_lastname = #lastname;
select tableB_id from tableB WHERE tableB_id = tableA_id";
db.QueryMultiple.(sqlString, new {lastname = "smith"});
Is something like this possible with Dapper or do I need a view or stored procedure to accomplish this? I can use multiple joins for one SQL statement, but in my real query there are 7 joins, and I didn't think I should return 7 objects.
Right now I'm just using object.
You can store every previous query in table parameter and then first perform select from the parameter and query for next, for example:
DECLARE #TableA AS Table(
tableA_id INT
-- ... all other columns you need..
)
INSERT #TableA
SELECT tableA_id
FROM tableA
WHERE tableA_lastname = #lastname
SELECT *
FROM #TableA
SELECT tableB_id
FROM tableB
JOIN tableA ON tableB_id = tableA_id
I've a problem with LINQ. Basically a third party database that I need to connect to is using the now depreciated text field (I can't change this) and I need to execute a distinct clause in my linq on results that contain this field.
I don't want to do a ToList() before executing the Distinct() as that will result in thousands of records coming back from the database that I don't require and will annoy the client as they get charged for bandwidth usage. I only need the first 15 distinct records.
Anyway query is below:
var query = (from s in db.tSearches
join sc in db.tSearchIndexes on s.GUID equals sc.CPSGUID
join a in db.tAttributes on sc.AttributeGUID equals a.GUID
where s.Notes != null && a.Attribute == "Featured"
select new FeaturedVacancy
{
Id = s.GUID,
DateOpened = s.DateOpened,
Notes = s.Notes
});
return query.Distinct().OrderByDescending(x => x.DateOpened);
I know I can do a subquery to do the same thing as above (tSearches contains unique records) but I'd rather a more straightfoward solution if available as I need to change a number of similar queries throughout the code to get this working.
No answers on how to do this so I went with my first suggestion and retrieved the unique records first from tSearch then constructed a subquery with the non unique records and filtered the search results by this subquery. Answer below:
var query = (from s in db.tSearches
where s.DateClosed == null && s.ConfidentialNotes != null
orderby s.DateOpened descending
select new FeaturedVacancy
{
Id = s.GUID,
Notes = s.ConfidentialNotes
});
/* Now filter by our 'Featured' attribute */
var subQuery = from sc in db.tSearchIndexes
join a in db.tAttributes on sc.AttributeGUID equals a.GUID
where a.Attribute == "Featured"
select sc.CPSGUID;
query = query.Where(x => subQuery.Contains(x.Id));
return query;
I want to perform a simple join on two tables (BusinessUnit and UserBusinessUnit), so I can get a list of all BusinessUnits allocated to a given user.
The first attempt works, but there's no override of Select which allows me to restrict the columns returned (I get all columns from both tables):
var db = new KensDB();
SqlQuery query = db.Select
.From<BusinessUnit>()
.InnerJoin<UserBusinessUnit>( BusinessUnitTable.IdColumn, UserBusinessUnitTable.BusinessUnitIdColumn )
.Where( BusinessUnitTable.RecordStatusColumn ).IsEqualTo( 1 )
.And( UserBusinessUnitTable.UserIdColumn ).IsEqualTo( userId );
The second attept allows the column name restriction, but the generated sql contains pluralised table names (?)
SqlQuery query = new Select( new string[] { BusinessUnitTable.IdColumn, BusinessUnitTable.NameColumn } )
.From<BusinessUnit>()
.InnerJoin<UserBusinessUnit>( BusinessUnitTable.IdColumn, UserBusinessUnitTable.BusinessUnitIdColumn )
.Where( BusinessUnitTable.RecordStatusColumn ).IsEqualTo( 1 )
.And( UserBusinessUnitTable.UserIdColumn ).IsEqualTo( userId );
Produces...
SELECT [BusinessUnits].[Id], [BusinessUnits].[Name]
FROM [BusinessUnits]
INNER JOIN [UserBusinessUnits]
ON [BusinessUnits].[Id] = [UserBusinessUnits].[BusinessUnitId]
WHERE [BusinessUnits].[RecordStatus] = #0
AND [UserBusinessUnits].[UserId] = #1
So, two questions:
- How do I restrict the columns returned in method 1?
- Why does method 2 pluralise the column names in the generated SQL (and can I get round this?)
I'm using 3.0.0.3...
So far my experience with 3.0.0.3 suggests that this is not possible yet with the query tool, although it is with version 2.
I think the preferred method (so far) with version 3 is to use a linq query with something like:
var busUnits = from b in BusinessUnit.All()
join u in UserBusinessUnit.All() on b.Id equals u.BusinessUnitId
select b;
I ran into the pluralized table names myself, but it was because I'd only re-run one template after making schema changes.
Once I re-ran all the templates, the plural table names went away.
Try re-running all 4 templates and see if that solves it for you.