ScalarQuery<int> query = new ScalarQuery<int>(typeof(Role),
"select count(role.RoleId) from Role as role");
return query.Execute();
It fails with the invalidcast exception but succeeds when count is replaced with max.
Edit: Some databases will return long for count queries. For example SQL Server.
ScalarQuery<long> query = new ScalarQuery<long>(typeof(Role),
"select count(r) from Role r");
return query.Execute();
What database are you using? Could be that count does not return an int.
Your could also try using http://api.castleproject.org/html/T_Castle_ActiveRecord_Queries_CountQuery.htm
Not exactly the answer to the question, but a recommendation: if you want to avoid the hassle of having to issue a query at all yourself, then just use ActiveRecordMediator<T>.Count() (which has overloads that take criteria / filter strings if you want a conditional count) and all return int against all databases.
Based on testing the answers given to date, the following worked for me (including a where clause):
// Option 1
int result = ActiveRecordMediator<Post>.Count("BlogId = ?", blogId);
// Option 2
CountQuery query = new CountQuery(typeof(Post), "BlogId = ?", blogId);
int result = ActiveRecordMediator.ExecuteQuery(query);
// Option 3
ScalarQuery<long> query= new ScalarQuery<long>(typeof(Post),
"SELECT COUNT(*) FROM Post WHERE BlogId = ?", blogId);
long result = query.Execute();
Related
I got two tables: comments and commentLikes
in the same query i count the likes users have given on a comment.
I got the following (simplified) query:
var res = (from c in db.Comments
where c.Topic.ID == topicID
select new
{
comment = c,
count = c.CommentLikes.Count()
}).ToList();
But, rather than mapping the likecount into the comment entity again, I'd like to get a list of Comments only with a field LikeCount in it, preferably with an efficient query. Something like this:
var res = (from c in db.Comments
where c.Topic.ID == topicID
select new
{
comment = c,
c.LikeCount = c.CommentLikes.Count()
}).ToList();
This query doesn't compile.
How to do this in linq?
You can't do that. EF does not support to project (= select) data into an entity. You must fill the LikeCount property in memory after the query has been executed. You can write it in a compact way, but it's basically just a foreach loop over the materialized anonymous objects:
IEnumerable<Comment> res =
(from c in db.Comments
where c.Topic.ID == topicID
select new
{
comment = c,
count = c.CommentLikes.Count()
})
.ToList() // DB query runs here, the rest in memory
.Select(a => {
a.comment.LikeCount = a.count;
return a.comment;
});
Is it possible to generate arbitrary where condtions SQL query through Jdbc template:
example:
If i pass value for 1 parameter (only name) : search by name
"select * from address where shopname = ?";
If i pass value for 2 parameter (name and city) - search by shopname and city:
"select * from address where shopname = ? and city = ?";
I have mupliple search fields. 7 fields. If user enters any combination. i have search only based on parameter. How to dynamically pass the parameters to the sql. Need snippet/Example how to achieve this.
What you want is some sort of criteria building api, which Hibernate has. Unfortunately, I don't think Spring's JdbcTemplate has any such facility. Others will correct me if I'm wrong...
Though as some guys already suggested that Hibernate is the best way of doing this, but still i think you can try this approach-
String sql = "select * from address where 1 = 1";
if(shopname != null)
sql += "and shopname = :shopname";
if(city!= null)
sql += "and city = :city";
and so on..and use NamedParameterJdbcTemplate
Spring Data and Hibernate have that kind of functionality. Though it might not be worth dragging in such big framework for your app.
You can try to check out SimpleJdbcInsert
http://docs.spring.io/spring/docs/current/spring-framework-reference/html/jdbc.html
Edit:
Alternatively you can try to fix it in SQL with checking on empty, but if you have lots of data to go through, this technique will slow down your request.
"select * from address
where (shopname = ? or shopname = null)
and (city = ? or city = null)";
If Scala is an option to you, the query could be constructed with something like this:
case class Search(shopname:String, city:String = None) {
def sql = "select * from address where shopname = '"+shopname+"'" + city.map(" and city = '"+
_ +"'").getOrElse("")
}
Example usage:
Search("lloh").sql
Search("lloh", Some("Austin")).sql
I want the the LINQ query result in int type variable.
i have a query this will always return the single int value. i want result sumthing like that.
int interlineId = from cSInterline in codeShareInterline_.AsEnumerable()
where cSInterline.Field<int>("InterCodeId") == interCodeId[0]
select cSInterline.Field<int>("PermitedPercent");
But it returning the error..
Your query is returning an IEnumerable<int>, with only one item in this case. So add Single or SingleOrDefault onto the end to return only that 1 item. If your query might return more than 1 item then use FirstOrDefault.
int interlineId =
(from cSInterline in codeShareInterline_.AsEnumerable()
where cSInterline.Field<int>("InterCodeId") == interCodeId[0]
select cSInterline.Field<int>("PermitedPercent")).SingleOrDefault();
Try this:
int interlineId = (from cSInterline in codeShareInterline_.AsEnumerable()
where cSInterline.Field<int>("InterCodeId") == interCodeId[0]
select cSInterline).Single().Field<int>("InterCodeId");
Try this (it should work):
int? interlineId = (from cSInterline in codeShareInterline_.AsEnumerable()
where cSInterline.Field<int>("InterCodeId") == interCodeId[0]
select cSInterline.Field<int>("PermitedPercent")).FirstOrDefault();
Is it possible to use JPQL for getting random rows? For example in SQL Server I would use:
select * from myTable where columnName = 4 order by newid()
Thanks,
Rod
This is what I use. I first get the number of rows for the entity and I then limit the results of the fetch query to a random row. This involves two queries, so if this is a problem for you you might want to watch native queries. If not here is the code I use:
public <T> T randomEntity(EntityManager em, Class<T> clazz) {
Query countQuery = em.createQuery("select count(id) from "+clazz.getName());
long count = (Long)countQuery.getSingleResult();
Random random = new Random();
int number = random.nextInt((int)count);
Query selectQuery = em.createQuery("from "+clazz.getName());
selectQuery.setFirstResult(number);
selectQuery.setMaxResults(1);
return (T)selectQuery.getSingleResult();
}
As of today (April 9th 2010), JPQL does not support random ordering
What do I put in my order by?? I want to order by Name. I have moved the orderby after the distinct because I read that it needs to be done last.
var result = (from r in db.RecordDocs
where r.RecordID == recordID
select new
{
DocTypeID = r.Document.DocType.DocTypeID,
Name = r.Document.DocType.Name,
Number = r.Document.DocType.Number
}
).Distinct().OrderBy( );
Just do
.OrderBy(doc => doc.Name)
Another option, if you really prefer the query expression syntax would be to chain your query construction across multiple statements:
var query = from r in db.RecordDocs
where r.RecordID == recordID
select new
{
DocTypeID = r.Document.DocType.DocTypeID,
Name = r.Document.DocType.Name,
Number = r.Document.DocType.Number
};
query = query.Disctinct();
query = from doc in query orderby doc.Name select doc;
Since all of these methods are deferred, this will result in the exact same execution performance.