I've got a search page with multiple inputs (text fields). These inputs may or may not be empty - depending on what the user is searching for.
In order to accommodate this I create a base searchQuery object that pulls in all the correct relationships, and then for each non-empty input I modify the query using the searchQuery.Where function.
If I place multiple conditions in the WHERE clause I get the following error:
Cannot compare elements of type 'System.Collections.Generic.ICollection`1'. Only primitive types, enumeration types and entity types are supported.
searchQuery = searchQuery.Where(Function(m) (
(absoluteMinimumDate < m.ClassDates.OrderBy(Function(d) d.Value).FirstOrDefault.Value) _
OrElse (Nothing Is m.ClassDates)
)
)
I know that code looks funky, but I was trying to format it so you didn't have to scroll horizontally to see it all
Now, if I remove the ORELSE clause, everything works (but of course I don't get the results I need).
searchQuery = searchQuery.Where(Function(m) (
(absoluteMinimumDate < m.ClassDates.OrderBy(Function(d) d.Value).FirstOrDefault.Value)
)
)
This one works fine
So, what am I doing wrong? How can I make a multi-condition where clause?
Multiple conditions in the Where isn't the problem. m.ClassDates Is Nothing will never be true and doesn't make sense in SQL terms. You can't translate "is the set of ClassDates associated with this record NULL?" into SQL. What you mean is, are there 0 of them.
If there are no attached ClassDate records, m.ClassDates will be an empty list. You want m.ClassDates.Count = 0 OrElse...
Related
I have a list of data with a title column (among many other columns) and I have a Power BI parameter that has, for example, a value of "a,b,c". What I want to do is loop through the parameter's values and remove any rows that begin with those characters.
For example:
Title
a
b
c
d
Should become
Title
d
This comma separated list could have one value or it could have twenty. I know that I can turn the parameter into a list by using
parameterList = Text.Split(<parameter-name>,",")
but then I am unsure how to continue to use that to filter on. For one value I would just use
#"Filtered Rows" = Table.SelectRows(#"Table", each Text.StartsWith([key], <value-to-filter-on>))
but that only allows one value.
EDIT: I may have worded my original question poorly. The comma separated values in the parameterList can be any number of characters (e.g.: a,abcd,foo,bar) and I want to see if the value in [key] starts with that string of characters.
Try using List.Contains to check whether the starting character is in the parameter list.
each List.Contains(parameterList, Text.Start([key], 1)
Edit: Since you've changed the requirement, try this:
Table.SelectRows(
#"Table",
(C) => not List.AnyTrue(
List.Transform(
parameterList,
each Text.StartsWith(C[key], _)
)
)
)
For each row, this transforms the parameterList into a list of true/false values by checking if the current key starts with each text string in the list. If any are true, then List.AnyTrue returns true and we choose not to select that row.
Since you want to filter out all the values from the parameter, you can use something like:
= Table.SelectRows(#"Changed Type", each List.Contains(Parameter1,Text.Start([Title],1))=false)
Another way to do this would be to create a custom column in the table, which has the first character of title:
= Table.AddColumn(#"Changed Type", "FirstChar", each Text.Start([Title],1))
and then use this field in the filter step:
= Table.SelectRows(#"Added Custom", each List.Contains(Parameter1,[FirstChar])=false)
I tested this with a small sample set and it seems to be running fine. You can test both and see if it helps with the performance. If you are still facing performance issues, it would probably be easier if you can share the pbix file.
This seems to work fairly well:
= List.Select(Source[Title], each Text.Contains(Parameter1,Text.Start(_,1))=false)
Replace Source with the name of your table and Parameter1 with the name of your Parameter.
I have the following function for a hacky project:
% The Record variable is some known record with an associated table.
Query = qlc:q([Existing ||
Existing <- mnesia:table(Table),
ExistingFields = record_to_fields(Existing),
RecordFields = record_to_fields(Record),
ExistingFields == RecordFields
]).
The function record_to_fields/1 simply drops the record name and ID from the tuple so that I can compare the fields themselves. If anyone wants context, it's because I pre-generate a unique ID for a record before attempting to insert it into Mnesia, and I want to make sure that a record with identical fields (but different ID) does not exist.
This results in the following (redacted for clarity) stack trace:
{aborted, {{case_clause, {stuff}},
[{db, '-my_func/2-fun-1-',8, ...
Which points to the line where I declare Query, however there is no case clause in sight. What is causing this error?
(Will answer myself, but I appreciate a comment that could explain how I could achieve what I want)
EDIT: this wouldn't be necessary if I could simply mark certain fields as unique, and Mnesia had a dedicated insert/1 or create/1 function.
For your example, I think your solution is clearer anyway (although it seems you can pull the record_to_fields(Record) portion outside the comprehension so it isn't getting calculated over and over.)
Yes, list comprehensions can only have generators and assignments. But you can cheat a little by writing an assignment as a one-element generator. For instance, you can re-write your expression as this:
RecordFields = record_to_fields(Record),
Query = qlc:q([Existing ||
Existing <- mnesia:table(Table),
ExistingFields <- [record_to_fields(Existing)],
ExistingFields == RecordFields
]).
As it turns out, the QLC DSL does not allow assignments, only generators and filters; as per the documentation (emphasis mine):
Syntactically QLCs have the same parts as ordinary list
comprehensions:
[Expression || Qualifier1, Qualifier2, ...]
Expression (the template)
is any Erlang expression. Qualifiers are either filters or generators.
Filters are Erlang expressions returning boolean(). Generators have
the form Pattern <- ListExpression, where ListExpression is an
expression evaluating to a query handle or a list.
Which means we cannot variable assignments within a QLC query.
Thus my only option, insofar as I know, is to simply write out the query as:
Query = qlc:q([Existing ||
Existing <- mnesia:table(Table),
record_to_fields(Existing) == record_to_fields(Record)
]).
I'm building a rails app for managing a queue of work items. I have several types of users ("access levels") to whom I want to auto-assign these work items.
The end goal is an "Auto-assign" button on one of my views that will automatically grab the next work item based on a priority, which is defined by the users's access level.
I'm trying to set up a class method in my work_item model to automatically sort work items by type based on the user's access level. I am looking at something like this:
def self.auto_assign_next(access_level)
case
when access_level = 2
where("completed = 'f'").order("requested_time ASC").limit(1)
when access_level > 2
where("completed = 'f'").order("CASE WHEN form='supervisor' THEN 1 WHEN form='installer' THEN 2 WHEN form='repair' THEN 3 WHEN form='mail' THEN 4 WHEN form='hp' THEN 5 ELSE 6 END").limit(1)
end
This isn't very DRY, though. Ideally I'd like the sort order to be configurable by administrators, so maybe setting up a separate table on which the sort order is kept would be best. The problem with that idea is that I have no idea how to pass the priority order on that table to the [postgre]SQL query. I'm new to SQL in general and somewhat lost with this one. Does anybody have any suggestions as to how this should be handled?
One fairly simple approach starts with turning your case statement into a new table, listing form values versus what precedence value they should be sorted by:
id | form | precedence
-----------------------------------
1 | supervisor | 1
2 | installer | 2
(etc)
Create a model for this, say, FormPrecedences (not a great name, but I don't totally grok your data model so pick one that better describes it). Then, your query can look like this (note: I'm assuming your current model is called WorkItems):
when access_level > 2
joins("LEFT JOIN form_precedences ON form_precedences.form = work_items.form")
.where("completed = 'f'")
.order("COALESCE(form_precedences.precedence, 6)")
.limit(1)
The way this works isn't as complicated as it looks. A "left join" in SQL simply takes all the rows of the table on the left (in this case, work_items) and, for each row, finds all the matching rows from the table on the right (form_precedences, where "matching" is defined by the bit after the "ON" keyword: form_precedences.form = work_items.form), and emits one combined row. If no match is found, a LEFT JOIN will still emit a row, but with all the right-hand values being NULL. A normal join would skip any rows with no right-hand match found.
Anyway, with the precedence data joined on to our work items, we can just sort by the precedence value. But, in case no match was found during the join above, that value will be NULL -- so, I use COALESCE (which returns the first of its arguments that's not NULL) to default to a precedence of 6.
Hope that helps!
I have a complex query that contains more than one place where the same primary key value must be substituted. It looks like this:
select Foo.Id,
Foo.BearBaitId,
Foo.LinkType,
Foo.BugId,
Foo.GooNum,
Foo.WorkOrderId,
(case when Goo.ZenID is null or Goo.ZenID=0 then
IsNull(dbo.EmptyToNull(Bar.FanName),dbo.EmptyToNull(Bar.BazName))+' '+Bar.Strength else
'#'+BarZen.Description end) as Description,
Foo.Init,
Foo.DateCreated,
Foo.DateChanged,
Bug.LastName,
Bug.FirstName,
Goo.BarID,
(case when Goo.ZenID is null or Goo.ZenID=0 then
IsNull(dbo.EmptyToNull(Bar.BazName),dbo.EmptyToNull(Bar.FanName))+' '+Bar.Strength else
'#'+BarZen.Description end) as BazName,
GooTracking.Status as GooTrackingStatus
from
Foo
inner join Bug on (Foo.BugId=Bug.Id)
inner join Goo on (Foo.GooNum=Goo.GooNum)
left join Bar on (Bar.Id=Goo.BarID)
left join BarZen on (Goo.ZenID=BarZen.ID)
inner join GooTracking on(Goo.GooNum=GooTracking.GooNum )
where (BearBaitId = :aBaitid)
UNION
select Foo.Id,
Foo.BearBaitId,
Foo.LinkType,
Foo.BugId,
Foo.GooNum,
Foo.WorkOrderId,
Foo.Description,
Foo.Init,
Foo.DateCreated,
Foo.DateChanged,
Bug.LastName,
Bug.FirstName,
0,
NULL,
0
from Foo
inner join Bug on (Foo.BugId=Bug.Id)
where (LinkType=0) and (BearBaitId= :aBaitid )
order by BearBaitId,LinkType desc, GooNum
When I try to use an integer parameter on this non-trivial query, it seems impossible to me. I get this error:
Error
Incorrect syntax near ':'.
The query works fine if I take out the :aBaitid and substitute a literal 1.
Is there something else I can do to this query above? When I test with simple tests like this:
select * from foo where id = :anid
These simple cases work fine. The component is TADOQuery, and it works fine until you add any :parameters to the SQL string.
Update: when I use the following code at runtime, the parameter substitutions are actually done (some glitch in the ADO components is worked around) and a different error surfaces:
adoFooContentQuery.Parameters.FindParam('aBaitId').Value := 1;
adoFooContentQuery.Active := true;
Now the error changes to:
Incorrect syntax near the keyword 'inner''.
Note again, that this error goes away if I simply stop using the parameter substitution feature.
Update2: The accepted answer suggests I have to find two different copies of the parameter with the same name, which bothered me so I reworked the query like this:
DECLARE #aVar int;
SET #aVar = :aBaitid;
SELECT ....(long query here)
Then I used #aVar throughout the script where needed, to avoid the repeated use of :aBaitId. (If the number of times the parameter value is used changes, I don't want to have to find all parameters matching a name, and replace them).
I suppose a helper-function like this would be fine too: SetAllParamsNamed(aQuery:TAdoQuery; aName:String;aValue:Variant)
FindParam only finds one parameter, while you have two with the same name. Delphi dataset adds each parameter as a separate one to its collection of parameters.
It should work if you loop through all parameters, check if the name matches, and set the value of each one that matches, although I normally choose to give each same parameter a follow-up number to distingish between them.
I'm trying to figure out the best approach to display combined tables based on matching logic and input search criteria.
Here is the situation:
We have a table of customers stored locally. The fields of interest are ssn, first name, last name and date of birth.
We also have a web service which provides the same information. Some of the customers from the web service are the same as the local file, some different.
SSN is not required in either.
I need to combine this data to be viewed on a Grails display.
The criteria for combination are 1) match on SSN. 2) For any remaining records, exact match on first name, last name and date of birth.
There's no need at this point for soundex or approximate logic.
It looks like what I should do is extract all the records from both inputs into a single collection, somehow making it a set on SSN. Then remove the blank ssn.
This will handle the SSN matching (once I figure out how to make that a set).
Then, I need to go back to the original two input sources (cached in a collection to prevent a re-read) and remove any records that exist in the SSN set derived previously.
Then, create another set based on first name, last name and date of birth - again if I can figure out how to make a set.
Then combine the two derived collections into a single collection. The collection should be sorted for display purposes.
Does this make sense? I think the search criteria will limit the number of record pulled in so I can do this in memory.
Essentially, I'm looking for some ideas on how the Grails code would look for achieving the above logic (assuming this is a good approach). The local customer table is a domain object, while what I'm getting from the WS is an array list of objects.
Also, I'm not entirely clear on how the maxresults, firstResult, and order used for the display would be affected. I think I need to read in all the records which match the search criteria first, do the combining, and display from the derived collection.
The traditional Java way of doing this would be to copy both the local and remote objects into TreeSet containers with a custom comparator, first for SSN, second for name/birthdate.
This might look something like:
def localCustomers = Customer.list()
def remoteCustomers = RemoteService.get()
TreeSet ssnFilter = new TreeSet(new ClosureComparator({c1, c2 -> c1.ssn <=> c2.ssn}))
ssnFilter.addAll(localCustomers)
ssnFilter.addAll(remoteCustomers)
TreeSet nameDobFilter = new TreeSet(new ClosureComparator({c1, c2 -> c1.firstName + c1.lastName + c1.dob <=> c2.firstName + c2.lastName + c2.dob}))
nameDobFilter.addAll(ssnFilter)
def filteredCustomers = nameDobFilter as List
At this point, filteredCustomers has all the records, except those that are duplicates by your two criteria.
Another approach is to filter the lists by sorting and doing a foldr operation, combining adjacent elements if they match. This way, you have an opportunity to combine the data from both sources.
For example:
def combineByNameAndDob(customers) {
customers.sort() {
c1, c2 -> (c1.firstName + c1.lastName + c1.dob) <=>
(c2.firstName + c2.lastName + c2.dob)
}.inject([]) { cs, c ->
if (cs && c.equalsByNameAndDob(cs[-1])) {
cs[-1].combine(c) //combine the attributes of both records
cs
} else {
cs << c
}
}
}