I have a table Customers with a CustomerId field, and a table of Publications with a PublicationId field. Finally, I have a mapping table CustomersPublications that records which publications a customer can access - it has two fields: CustomerId field PublicationId.
For a given customer, I want to update the CustomersPublications table based on a list of publication ids. I want to remove records in CustomersPublications where the PublicationId is not in the list, and add new records where the PublicationId is in the list but not already in the table.
This would be easy in SQL, but I can't figure out how to do it in Linq.
For the delete part, I tried:
var recordsToDelete = dataContext.CustomersPublications.Where
(
cp => (cp.CustomerId == customerId)
&& ! publicationIds.Contains(cp.PublicationId)
);
dataContext.CustomersPublications.DeleteAllOnSubmit(recordsToDelete);
... but that didn't work. I got an error:
System.NotSupportedException: Method 'Boolean Contains(Int32)' has no supported translation to SQL
So, I tried using Any(), as follows:
var recordsToDelete = dataContext.CustomersPublications.Where
(
cp => (cp.CustomerId == customerId)
&& ! publicationIds.Any(p => p == cp.PublicationId)
);
... and this just gives me another error:
System.NotSupportedException: Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains() operator
Any pointers?
[I have to say, I find Linq baffling (and frustrating) for all but the simplest queries. Better error messages would help!]
Wow. Almost by chance, I discovered that the reason I couldn't use Contains in my first example was that my publicationIds was an IList<int> rather than a an int[]. I changed it, and it worked.
Thanks, compiler message author! :-|
Related
I have a table in my MySQL database, compatibility_core_rules, which essentially stores pairs of ids which represent compatibility between parts which have fields with those corresponding ids. Now, my aim is to get all possible compatibility pairs by following the transitivity of the pairs (e.g. so if the table has (1,2) and (2,4), then add the pair (1,4)). So, mathematically speaking, I'm trying to find the transitive closure of the compatibility_core_rules table.
E.g. if compatibility_core_rules contains (1,2), (2,4) and (4,9), then initially we can see that (1,2) and (2,4) gives a new pair (1,4). I then iterate over the updated pairs and find that (4,9) with the newly added (1,4) gives me (1,9). At this point, iterating again would add no more pairs.
So my approach is to create a view with the initial pairs from compatibility_core_rules, like so:
CREATE VIEW compatibility_core_rules_closure
AS
SELECT part_type_field_values_id_a,
part_type_field_values_id_b,
custom_builder_id
FROM compatibility_core_rules;
Then, in order to iteratively discover all pairs, I need to keep replacing that view with an updated version of itself that has additional pairs each time. However, I found MySQL doesn't like me referencing the view in its own definition, so I make a temporary view (with or replace, since this will be inside a loop):
CREATE OR REPLACE VIEW compatibility_core_rules_closure_temp
AS
SELECT part_type_field_values_id_a,
part_type_field_values_id_b,
custom_builder_id
FROM compatibility_core_rules_closure;
No problems here. I then reference this temporary view in the following CREATE OR REPLACE VIEW statement to update the compatibility_core_rules_closure view with one iteration's worth of additional pairs:
CREATE OR REPLACE VIEW compatibility_core_rules_closure
AS
SELECT
CASE WHEN ccr1.part_type_field_values_id_a = ccr2.part_type_field_values_id_a THEN ccr1.part_type_field_values_id_b
WHEN ccr1.part_type_field_values_id_a = ccr2.part_type_field_values_id_b THEN ccr1.part_type_field_values_id_b
END ccrA,
CASE WHEN ccr1.part_type_field_values_id_a = ccr2.part_type_field_values_id_a THEN ccr2.part_type_field_values_id_b
WHEN ccr1.part_type_field_values_id_a = ccr2.part_type_field_values_id_b THEN ccr2.part_type_field_values_id_a
END ccrB,
ccr1.custom_builder_id custom_builder_id
FROM compatibility_core_rules_closure_temp ccr1
INNER JOIN compatibility_core_rules_closure_temp ccr2
ON (
ccr1.part_type_field_values_id_a = ccr2.part_type_field_values_id_a OR
ccr1.part_type_field_values_id_a = ccr2.part_type_field_values_id_b
)
GROUP BY ccrA,
ccrB
HAVING -- ccrA and ccrB are in fact not the same
ccrA != ccrB
-- ccrA and ccrB do not belong to the same part type
AND (
SELECT ptf.part_type_id
FROM part_type_field_values ptfv
INNER JOIN part_type_fields ptf
ON ptfv.part_type_field_id = ptf.id
WHERE ptfv.id = ccrA
LIMIT 1
) !=
(
SELECT ptf.part_type_id
FROM part_type_field_values ptfv
INNER JOIN part_type_fields ptf
ON ptfv.part_type_field_id = ptf.id
WHERE ptfv.id = ccrB
LIMIT 1
)
Now this is where things go wrong. I get the following error:
#1146 - Table 'db509574872.compatibility_core_rules_closure' doesn't exist
I'm very confused by this error message. I literally just created the view/table only two statements ago. I'm sure the SELECT query itself is correct since if I try it by itself and it runs fine. If I change the first line to use compatibility_core_rules_closure2 instead of compatibility_core_rules_closure then it runs fine (however, that's not much use since I need to be re-updating the same view again and again). I've looked into the SQL SECURITY clauses but have not had any success. Also been researching online but not getting anywhere.
Does anyone have any ideas what is happening and how to solve it?
MySQL doesn't support sub-queries in views.
You'll have to separate them... ie. using another view containing the sub-query inside you main view.
Running the create statement for that view will render an error, not creating it, hence the doesn't exist error you're getting when querying it.
before i use alias for table i get the error:
: Integrity constraint violation: 1052 Column 'id' in field list is ambiguous
Then i used aliases and i get this error:
unknown index a
I am trying to get a list of category name ( dependant to a translation) and the associated category id which is unique. Since i need to put them in a select, i see that i should use the lists.
$categorie= DB::table('cat as a')
->join('campo_cat as c','c.id_cat','=','a.id')
->join('campo as d','d.id','=','c.id_campo')
->join('cat_nome as nome','nome.id_cat','=','a.id')
->join('lingua','nome.id_lingua','=','lingua.id')
->where('lingua.lingua','=','it-IT')
->groupby('nome.nome')
->lists('nome.nome','a.id');
The best way to debug your query is to look at the raw query Laravel generates and trying to run this raw query in your favorite SQL tool (Navicat, MySQL cli tool...), so you can dump it to log using:
DB::listen(function($sql, $bindings, $time) {
Log::info($sql);
Log::info($bindings);
});
Doing that with yours I could see at least one problem:
->where('lingua.lingua','=','it-IT')
Must be changed to
->where('lingua.lingua','=',"'it-IT'")
As #jmail said, you didn't really describe the problem very well, just what you ended up doing to get around (part of) it. However, if I read your question right you're saying that originally you did it without all the aliases you got the 'ambiguous' error.
So let me explain that first: this would happen, because there are many parts of that query that use id rather than a qualified table`.`id.
if you think about it, without aliases you query looks a bit like this: SELECT * FROM `cat` JOIN `campo_cat` ON `id_cat` = `id` JOIN `campo` ON `id` = `id_campo`; and suddenly, MySQL doesn't know to which table all these id columns refer. So to get around that all you need to do is namespace your fields (i.e. use ... JOIN `campo` ON `campo`.`id` = `campo_cat`.`id_campo`...). In your case you've gone one step further and aliased your tables. This certianly makes the query a little simpler, though you don't need to actually do it.
So on to your next issue - this will be a Laravel error. And presumably happening because your key column from lists($valueColumn, $keyColumn) isn't found in the results. This is because you're referring to the cat.id column (okay in your aliased case a.id) in part of the code that's no longer in MySQL - the lists() method is actually run in PHP after Laravel gets the results from the database. As such, there's no such column called a.id. It's likely it'll be called id, but because you don't request it specifically, you may find that the ambiguous issue is back. My suggestion would be to select it specifically and alias the column. Try something like the below:
$categories = DB::table('cat as a')
->join('campo_cat as c','c.id_cat','=','a.id')
->join('campo as d','d.id','=','c.id_campo')
->join('cat_nome as nome','nome.id_cat','=','a.id')
->join('lingua','nome.id_lingua','=','lingua.id')
->where('lingua.lingua','=','it-IT')
->groupby('nome.nome')
->select('nome.nome as nome_nome','a.id as a_id') // here we alias `.id as a_id
->lists('nome_nome','a_id'); // here we refer to the actual columns
It may not work perfectly (I don't use ->select() so don't know whether you pass an array or multiple parameters, also you may need DB::raw() wrapping each one in order to do the aliasing) but hopefully you get my meaning and can get it working.
This one is a pretty good one IMO and I have not seen a close exampled on SO or Google so here you go. I need to do the following within a Perl application I am building. Unfortunately it can not be done directly in MySQL and will require DBI. In a nutshell I need to take Database1.tableA and locate every record with the column 'status' matching 'started'. This I can do as it is fairly easy (not very good with DBI yet, but have read the docs), but where I am having issues is what I have to do next.
my $started_query = "SELECT primary_ip FROM queue WHERE status='started'";
my $started = $dbh->prepare($started_query);
$started->execute();
while ( my #started = $started->fetchrow_array() ) {
# Where I am hoping to have the following occur so it can go by row
# for only rows with the status 'started'
}
So for each record in the #started array, really only contains one value per iteration of the while loop, I need to see if it exists in the Database2.tableA and IF it does exist in the other database (Database2.tableA) I need to delete it from Database1.tableA, but if it DOES NOT exist in the other database (Database2.tableA) I need to update the record in the current database (Database1.tableA).
Basically replicating the below semi-valid MySQL syntax.
DELETE FROM tableA WHERE primary_ip IN (SELECT primary_ip FROM db2.tablea) OR UPDATE tableA SET status = 'error'
I am limited to DBI to connect to the two databases and the logic is escaping me currently. I could do the queries to both databases and store in #arrays and then do a comparison, but that seems redundant as I think it should be possible within the while ( my #started = $started->fetchrow_array() ) as that will save on runtime and resources required. I am also not familiar enough with passing variables between DBI instances and as the #started array will always contain the column value I need to query for and delete I would like to take full advantage of having that defined and passed to the DBI objects.
I am going to be working on this thing all night and already ran through a couple pots of coffee so your helping me understand this logic is greatly appreciated.
You'll be better off with fetchrow_hashref, which returns a hashref of key/value pairs, where the keys are the column names, rather than coding based on columns showing up at ordinal positions in the array.
You need an additional database handle to do the lookups and updates because you've got a live statement handle on the first one. Something like this:
my $dbh2 = DBI->connect(...same credentials...);
...
while(my $row = $started->fetchrow_hashref)
{
if(my $found = $dbh2->selectrow_hashref("SELECT * FROM db2.t2 WHERE primary_ip = ?",undef,$row->{primary_ip}))
{
$dbh2->do("DELETE FROM db1.t1 WHERE primary_ip = ?",undef,$found->{primary_ip});
}
else
{
$dbh2->do("UPDATE db1.t1 SET status = 'error' WHERE primary_ip = ?",undef,$found->{primary_ip}");
}
}
Technically, I don't "need" to fetch the row from db2.t2 into my $found since you're only apparently testing for existence, there are other ways, but using it here is a bit of insurance against doing something other than you intended, since it will be undef if we somehow get some bad logic going and that should keep us from making some potential wrong changes.
But approaching a relational database with loop iterations is rarely the best tactic.
This "could" be done directly in MySQL with just a couple of queries.
First, the updates, where t1.status = 'started' and t2.primary_ip has no matching value for t1.primary_ip:
UPDATE db1.t1 a LEFT JOIN db2.t2 b ON b.primary_ip = a.primary_ip
SET a.status = 'error'
WHERE b.primary_ip IS NULL AND a.status = 'started';
If you are thinking "but b.primary_ip is never null" ... well, it is null in a left join where there are no matching rows.
Then deleting the rows from t1 can also be accomplished with a join. Multi-table joins delete only the rows from the table aliases listed between DELETE and FROM. Again, we're calling "t1" by the alias "a" and t2 by the alias "b".
DELETE a
FROM db1.t1 a JOIN db2.t2 b ON a.primary_ip = b.primary_ip
WHERE a.status = 'started';
This removes every row from t1 ("a") where status = 'started' AND where a matching row exists in t2.
I am trying to do a join in linq , however for some reason I can't access the primary key of a table. It's the 'h.ProjectId' that doesn't seem to be accepted.
The following error is given
CW1.SearchWebService.Bid does not contain a definition for 'ProjectId' and no extention method 'ProjectId' accepting a first argument of type 'CW1SearchWebService.Bid'
Code:
var allProjects = ctxt.Project.ToList() ;
var allBids = ctxt.Bid.ToArray();// return all bids
var projects = (from project in allProjects join h in allBids
on
project.ProjectId equals h.ProjectId)
The problem, according to your error message, is the h.ProjectId. The error message says that the "Bid" class (CW1.SearchWebService.Bid) does not contain a member ProjectId, so the statement fails.
You should revisit your classes, and see what the proper join option would be. If you are sure that field should be in the table, you may need to regenerate your schema.
Perhaps the LINQ schema was generated before the field was added to the database. If it was generated with sqlmetal, try running sqlmetal over your database again. Otherwise just add it using the designer.
I have a few rows of data pulled into business objects via linq-to-sql from large tables.
Now I want to get a few rows that don't match to test my comparison functions.
Using what I thought would work I get a NotSupportedException:
Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains() operator.
Here's the code:
//This table has a 2 field primary key, the other has a single
var AllNonMatches = from c in dc.Acaps
where !Matches.Rows.Any((row) => row.Key.Key == c.AppId & row.Key.Value == c.SeqNbr)
select c;
foreach (var item in AllNonMatches.Take(100)) //Exception here
{}
The table has a compound primary key: AppId and SeqNbr.
The Matches.Rows is defined as a dictionary of keyvaluepair(appid,seqnbr).
and the local sequence it is referring to appears to be the local dictionary.
Could you provide more information on the structure and the name(s) of the table(s) plz?
Not sure what you're trying to do...
edit:
Ok.. I think I get it now...
It appears you can't merge/join local tables (dictionary) with a SQL table.
If you can, I'm afraid I don't know how to do it.
The simplest solution I can think of is to put those results in a table ("Match" for instance) with foreign keys related to your table "Acaps" and then use linq-to-sql, like:
var AllNonMatches = dc.Acaps.Where(p=>p.Matchs==null).Take(100).ToList();
Sorry I couldn't come up with any better =(
What about this:
var AllNonMatches = from c in dc.Acaps
where !(Matches.Rows.ContainsKey(c.AppId) && Matches.Rows.ContainsValue(c.SeqNbr))
select c;
That will work fine. I have also used a bitwise AND operator (&&) - I think thats the right term to help improve performance over the standard AND operator.