I have a problem in generating an Entity Framework query and not okay with linq style one :.....
This is my attempt:
var query = db.table
.Where(x => x.colA == 1)
.GroupBy(x => new {x.min,x.max})
.Select(y => if(y.key.min==0 && y.key.max==0)
{ " unchanged " }
else
{ y.key.min.tostring()+" "+y.key.max.tostring() })
.ToList()
I want to get "unchanged" string, if both value ofmin and max are zero, otherwise concat them
Use the conditional operator
// ...
.Select(y=> y.key.min==0 && y.key.max==0
? " unchanged "
: y.key.min.tostring()+" "+y.key.max.tostring())
// ...
Apparently all elements in your table have properties min and max
After GroupBy(x=> new {x.min,x.max}) you'll have a sequence of groups, where each group has a key {min, max}, all elements in the group have this value for their min and max properties.
After the GroupBy, you take every group, and from every group you'll select exactly one string. You get rid of the element of the group.
The string that you select depends on the key of the group: if the key = {0, 0} you select the string "unchanged", else you select the string:
y.key.min.tostring()+" "+y.key.max.tostring()
The result is a list of strings, something like:
"3 7",
"4 10,
"unchanged",
"2 8",
Are you sure you want this?
In that case you won't need the GroupBy. Distinct will be simpler and faster
List<string> result = db.table
.Where(tableRow => tableRow.colA == 1)
.Select(tableRow => tableRow.min==0 && tableRow.max==0
? " unchanged "
: tableRow.min.tostring()+" "+tableRow.max.tostring())
// from here you have a sequence of strings
// get rid of duplicates:
.Distinct()
.ToList();
For this specific case, you can use Conditional Operator (?:)
var query = db.table
.Where(x=> x.colA == 1)
.GroupBy(x=> new {x.min,x.max})
.Select(y=> (y.Key.min == 0 && y.Key.max == 0) ? " unchanged" : (y.Key.min.ToString()+" "+y.Key.max.ToString()))
.ToList();
Sorry I can't try it right now, but i think this should work
var query = db.table
.Where(x=> x.colA == 1)
.GroupBy(x=> new {x.min,x.max})
.Select(y=> {if(y.key.min==0 && y.key.max==0)
{
" unchanged "
} else
{
y.key.min.tostring()+" "+y.key.max.tostring();
} return y;})
.ToList()
Related
When building a complex SQL query for Laravel, using ? as placeholders for parameters is great. However when the value is null, the SQL syntax needs to be changed from = ? to IS NULL. Plus, since the number of parameters is one less, I need to pass a different array.
To get it to work, I have written it like this, but there must be a better way:
if ($cohortId === null) {
// sql should be: column IS NULL
$sqlCohortString = "IS NULL";
$params = [
Carbon::today()->subDays(90),
// no cohort id here
];
} else {
// sql should be: column = ?
$sqlCohortString = "= ?";
$params = [
Carbon::today()->subDays(90),
$cohortId
];
}
$query = "SELECT items.`name`,
snapshots.`value`,
snapshots.`taken_at`,
FROM snapshots
INNER JOIN (
SELECT MAX(id) AS id, item_id
FROM snapshots
WHERE `taken_at` > ?
AND snapshots.`cohort_id` $sqlCohortString
GROUP BY item_id
) latest
ON latest.`id` = snapshots.`id`
INNER JOIN items
ON items.`id` = snapshots.`item_id`
ORDER by media_items.`slug` ASC
";
$chartData = DB::select($query, $params);
My question is: does Laravel have a way to detect null values and replace ? more intelligently?
PS: The SQL is for a chart, so I need the single highest snapshot value for each item.
You can use ->when to create a conditional where clause:
$data = DB::table('table')
->when($cohortId === null, function ($query) {
return $query->whereNull('cohort_id');
}, function ($query) use ($cohortId) {
// the "use" keyword provides access to "outer" variables
return $query->where('cohort_id', '=', $cohortId);
})
->where('taken_at', '>', $someDate)
->toSql();
I was trying to convert a query from SQL into Scala code with Slick, but I have got a compiler error in filter clause: constructor cannot be instantiated to expected type.
My code in Slick:
val subquery = (for {
pit <- PassInTripTable.table
t <- TripTable.table if pit.tripNoFk === t.tripNo
} yield (pit, t))
.map{ case (pit, t) => ( pit, Case.If(t.townFrom <= t.townTo).Then(t.townFrom ++ t.townTo).Else(t.townFrom ++ t.townTo) )}
.groupBy(_._1.idPsgFk)
.filter{ case ((pit, count), group) => ( group.map(_._2).countDistinct === 1)}
.map(_._1)
val query = PassengerTable.table.filter(_.idPsg in subquery).map(_.name)
db.run(query.result)
The query in SQL itself:
select name from passenger
where id_psg in
(
select id_psg from trip t,pass_in_trip pit
where t.trip_no=pit.trip_no
group by id_psg
having count(distinct case when town_from<=town_to then town_from+town_to else town_to+town_from end)=1
)
I would be very grateful if someone helped me to find an error.
From looking at your code, it looks like the type you are matching on is not supposed to be "((pit, count), group)".
groupBy in Slick only returns a collection of Tuple2s.
http://slick.lightbend.com/doc/3.0.0/queries.html
So, the filter might look something like...
.filter{ case (pit, count) => ( count.map(_._2).countDistinct === 1)}
The problem is that Slick .groupBy requires a .map call with aggregating functions afterwards. You can find detailed information here.
So, try this:
.groupBy(_._1.idPsgFk)
.map{ case (key, group) => (key, group.map(_._2).countDistinct)}
.filter{ case (_, count) => count === 1}
.map(_._1)
P.S.
I've also found "bad smells" in your code. You get pairs as a result of for-comrehension, but it looks like standard join would be more appropriate here (and more efficient), something like:
PassInTripTable.table.join(TripTable.table).on(_.tripNoFk === _.tripNo)
.map{ case (pit, t) => ...}
And why would you use such condition:
Case.If(t.townFrom <= t.townTo).Then(t.townFrom ++ t.townTo).Else(t.townFrom ++ t.townTo)? Its branches are the same, so equals to t.townFrom ++ t.townTo.
This is my lambda to get the data from pub_page_menustructur
DataHelper.DataObj.QueryTable(SystemType.H0, p=>p.PARENTID == null) this is the lambda expression i had write. it have the same effection as "select * from pub_page_menustructur where parentid = null" show in the picture. is there any other way to show as "parentid is null"
This way work for you if you are using Entity Framework
var result = dbcontext.PUB_PAGE_MANUSTRUCTURE.Where(w => w.PARENTID == null).ToList();
the answer is
var result = dbcontext.PUB_PAGE_MANUSTRUCTURE.Where(w => w.PARENTID.Trim() == null).ToList();
I have two tables employee_personals where all the personal record of the employee is stored and telephone_bills where the telephone bills paid to a particular employee is stored for each month. Now in my employeePersonalsController.php I have a function called api_show_employees() which is similar to below :
function api_show_employees() {
//$this->autoRender = false;
//Configure::write("debug",0);
$office_id = '';
$cond = '';
if(isset($_GET['office_id']) && trim($_GET['office_id']) != '') {
$office_id = $_GET['office_id'];
$cond['EmployeePersonal.office_id'] = $office_id;
}
if(isset($_GET['telephoneBillTo']) && isset($_GET['telephoneBillFrom']) ) {
if($_GET['telephoneBillTo'] != '' && $_GET['telephoneBillFrom'] != '') {
$cond['TelephoneBill.bill_from'] = $_GET['telephoneBillFrom'];
$cond['TelephoneBill.bill_to'] = $_GET['telephoneBillTo'];
}
}
$order = 'EmployeePersonal.name';
// $employee = $this->EmployeePersonal->find('all');
$employee = $this->EmployeePersonal->find('all',array('order' => $order,'conditions'=>$cond));
//return json_encode($employee);
}
This functions basically finds all the employees who paid bills in the given period. But I am getting an error
Error: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'TelephoneBill.bill_from' in 'where clause'
Models : EmployeePersonal.php:
var $hasMany = array(
'TelephoneBill' => array(
'className' => 'TelephoneBill',
)
);
TelephoneBill.php
public $name = 'TelephoneBill';
var $hasMany = array('EmployeePersonal');
NB: If I skip the bill_from and bill_to conditions, I am getting the results , with TelephoneBill array !
TLDR: use Joins instead.
Details/Notes:
1) it looks like you're using recursive. Don't do that. Use Containable instead.
2) You can't limit the parent model based on conditions against data from a contained/recursive-included table - instead, use Joins.
2b) Or, you could query from the other direction, and query your TelephoneBill with conditions, then contain the EmployeePersonal.
I don't know how to work with nested selects in LINQ.
How could I convert this SQl expression to LINQ?
Select i.ID, i.Impression,
(Select COUNT(ImpressionsId)
from DiaryImpressions
where DiaryPostsId = '2' AND ImpressionsId = i.ID) as Num from Impressions i
Seriously? DiaryPostsId is a string? Oh well...
from i in context.Impressions
select new {
i.ID,
i.Impressions,
Num = (from d in context.DiaryImpressions
where d.DiaryPostsId == "2"
&& d.ImpressionsId == i.ID
select d).Count()
}
from ...
select new {
i.Id,
i.Impression,
Count = context.DiaryImpressions.Count(d => d.DiaryPostsId == 2 && d.ImpressionsId == i.Id)
}
If you map your objects properly, you can use child relations directly:
Count = i.DiaryImpressions.Count(d => d.DiaryPostsId == 2)