I need to do something like this,
My two tables have the same signature, but different class so It suppose to work but it is not working.
var myTable;
if (booleanVariable == true)
{
myTable = table1;
}
else
{
myTable = table2;
}
var myLinq1 = from p in myTable
join r in myOtherTable
select p;
In this case, I have to initialize myTable
I have tried also,
var myTable= table2;
if (booleanVariable == true)
{
myTable = table1;
}
var myLinq1 = from p in myTable
join r in myOtherTable
select p;
then var is type table2, then it can't be changed to table1 type.
I need help, I don't want to make a copy paste of all the code. the linq query is huge, and it s nested with 5 or 6 queries. also I have to do this on 12 different methods.
Thanks a lot for your help.
Don't know if this will work, never tried it, but...
If both classes can implement the same interface or share a base class, could you maybe do:
var q = (booleanVariable)
? from p in myTable1 select (ISomeInterface)p
: from p in myTable2 select (ISomeInterface)p;
If you use this often, you can put this into its own method - I believe it will return IQueryable<ISomeInterface>.
Then connect to the rest of the LINQ query using the LINQ methods instead of the LINQ C# syntax (i.e. OrderBy() instead of orderby). I just don't know if LINQ-to-SQL will be smart enough to translate this into the correct SQL query.
But I agree with Jon's comment - this is probably bad design, and should be revisited. If you can't reorganize the tables themselves, and if you only need read access, how about a view that unions the two tables together, then tie that view into your LINQ-to-SQL structure.
Related
i am having troubles understanding how to access columns from a subquery (MySQL). Here is my code:
Personne personne = Personne.PERSONNE.as("personne");
Evenement evenement = Evenement.EVENEMENT.as("evenement");
Genealogie genealogie = Genealogie.GENEALOGIE.as("genealogie");
Lieu lieu = Lieu.LIEU.as("lieu");
SelectField<?>[] select = { DSL.countDistinct(personne.ID).as("countRs"), lieu.LIBELLE.as("libelleRs"),
lieu.ID.as("idVille") };
Table<?> fromPersonne = evenement.innerJoin(personne).on(personne.ID.eq(evenement.IDPERS))
.innerJoin(genealogie).on(genealogie.ID.eq(personne.IDGEN)).innerJoin(lieu)
.on(lieu.ID.eq(evenement.IDLIEU));
Table<?> fromFamille = evenement.innerJoin(personne).on(personne.IDFAM.eq(evenement.IDFAM))
.innerJoin(genealogie).on(genealogie.ID.eq(personne.IDGEN)).innerJoin(lieu)
.on(lieu.ID.eq(evenement.IDLIEU));
GroupField[] groupBy = { lieu.ID };
Condition condition = //conditionally build, not relevant i think
result = create.select(DSL.asterisk())
.from(create.select(select).from(fromPersonne).where(condition).groupBy(groupBy)
.union(create.select(select).from(fromFamille).where(condition).groupBy(groupBy)))
// i would like something like this but i don't know how: .groupBy(groupBy).fetch();
Basicly what i have is:
SELECT
*
FROM(
(SELECT
countRs, libelleRs, idVille
FROM
fromPersonne
WHERE
-- conditions
GROUP BY lieu.ID)
UNION
(SELECT
countRs, libelleRs, idVille
FROM
fromFamille
WHERE
-- conditions
GROUP BY lieu.ID)
)GROUP BY lieu.ID -- this is where i need help
In a plain MySQL query i would just give an alias to the union and then make a reference to the column i want to group by using the alias but it seems like it does not work like this with JOOQ.
I just need to group the results of the subqueries together but i don't know how to make a reference to the subqueries columns... I am sure i would have to reference my subqueries in objects outside of that "main select" to be able to access the columns or something along those lines but i am lost in all the object types.
You have to assign your derived table to a local variable and dereference columns from it, e.g.
Table<?> t = table(
select(...).from(...).groupBy(...).unionAll(select(...).from(...).groupBy(...))
).as("t");
Field<Integer> tId = t.field(lieu.ID);
First of all, I understand why I'm getting this error message, and I know of a way to solve it, but I'm hoping for something more efficient than what I have in mind. Here is basically what I have:
UPDATE customer c
JOIN customer d ON c.customer_id = d.parent_customer_id
SET ?
WHERE d.customer_type = "Big Cheese";
So, the data being fed in to the "?" parameter looks like this:
{"customer_id": 10, "customer_name": "Cheese-It", ... }
The problem is, since I'm joining on a table that is basically itself, all of the columns have the same name. The only way I know how to fix this is edit the JSON and prefix all of the fields with the alias it needs:
{"c.customer_id": 10, "c.customer_name": "Cheese-It", ... }
I was hoping for a more elegant way of going about this. Is there a way to refactor my SQL so that it knows which table alias I want to update? Any ideas?
A subquery will do what you are wanting, but it's actually less efficient, as subqueries inside the WHERE clause are generally performance killers. I feel like you have to be parsing the JSON into SQL, so I would simply add the alias at that point.
Anyway, for reference, here's how you can refactor the SQL to not need an alias:
UPDATE customer
SET ?
WHERE customer_id IN (
SELECT c.customer_id
FROM customer c
JOIN customer d ON c.customer_id = d.parent_customer_id
WHERE d.customer_type = 'Big Cheese'
);
NOTE: this is untested
EDIT:
On second thought, an EXISTS clause would be slightly better for performance:
UPDATE customer c
SET ?
WHERE EXISTS (
SELECT 1
FROM customer d
WHERE d.parent_customer_id = c.customer_id
AND d.customer_type = 'Big Cheese'
);
Either way should work. As long as you don't have a JOIN in the update, there is only one table the SET columns can reference, so you will avoid the ambiguous column name error.
I know this is an older question, but I found a better solution that doesn't have the performance hit. You can add the alias to your property names in the object you're updating.
Here is the helper function to translate the standard property names with an alias.
const allowUpdate = ['name']
function addUpdateAlias(updated, alias) {
let validUpdate = {}
for (let p in updated) {
if (allowUpdate.indexOf(p) > -1) {
validUpdate[`${alias}.${p}`] = updated[p]
}
}
return validUpdate;
}
Now wrap the object you want to update with the function above and the alias is applied in the update!
Your parameters would then be: [addUpdateAlias(customer, 'c')] to pass into your original query.
For example if I had an IQueryable of Person objects and each Person had an Age ID and I wanted to make another query that selected all rows from a table that contains an integer ID that was in this IQueryable of IDs...
Could I use something like this?
List<int> AgeList = new List<int>();
foreach(Person p in Persons)
{
AgeList.Add(p.Age);
}
var ageStats = from a in db.Ages
where AgeList.Contains(a.Age)
select a;
Or what would be a better way so I didn't need to loop?
Thanks
It sounds like you want to perform a join. Since you mentioned that Persons is an IQueryable, is it coming from the database as well?
Either a join or SelectMany (which translates to a join in LINQ to SQL) should suffice.
Join:
var ageStats = from a in db.Ages
join p in db.Persons on a.Age equals p.Age
select a;
SelectMany:
var ageStats = from a in db.Ages
from p in db.Persons
where a.Age == p.Age
select a;
You can do
List<int> AgeList = Persons.Select(p => p.Age);
However, even tho the msdn page for .Select does not say much, I'm pretty sure .Select still is a loop, so you won't really gain any performance by writing it like that
var ageStats = from a in db.Ages
where Persons.Select(p => p.Age).Contains(a.Age)
select a;
It's been a while since I've written raw SQL, I was hoping someone could help me out in optimizing this SQL query so that it works across, both, MySQL and PostgreSQL.
I would also have to implement this via CodeIgniter (2.x) using ActiveRecord, any help/advice?
SELECT *
FROM notaries, contact_notaries
WHERE notaries.id = contact_notaries.notary_id
AND WHERE ( contact_notaries.city LIKE %$criteria%
OR contact_notaries.state LIKE %$criteria
OR contact_notaries.address LIKE %$criteria%)
Thanks!
Each query can have just one WHERE clause (you don't need the second)
It's much better to put join condition into JOIN rather then WHERE.
Are you sure you really need all the columns from 2 tables (*)?
So I'd refactor it to
SELECT [field_list]
FROM notaries
INNER JOIN contact_notaries ON (notaries.id = contact_notaries.notary_id)
WHERE ( contact_notaries.city LIKE '%$criteria%'
OR contact_notaries.state LIKE '%$criteria'
OR contact_notaries.address LIKE '%$criteria%')
Using a1ex07's query:
SELECT [field_list]
FROM notaries
INNER JOIN contact_notaries ON (notaries.id = contact_notaries.notary_id)
WHERE ( contact_notaries.city LIKE '%$criteria%'
OR contact_notaries.state LIKE '%$criteria'
OR contact_notaries.address LIKE '%$criteria%')
Active record:
$this->db->select(); // Leave empty to select all fields
$this->db->join('contact_notaries', 'notaries.id = contact_notaries.notary_id', 'inner');
$this->db->like('contact_notaries.city', 'criteria');
$this->db->like('contact_notaries.state', 'criteria');
$this->db->like('contact_notaries.address', 'match');
$results = $this->db->get('notaries');
To specify a list of fields you can do $this->db->select('field_1, field_2, ...');.
http://codeigniter.com/user_guide/database/active_record.html
I have a MySql db with innoDB tables. Very simplified this is how two tables are layed out:
Table A:
controlID(PK)
controlText
Table B:
controlOptionID(pk)
controlID(FK to table A)
controlOptionType
controlOptionValue
So many controlOptions(table B) can reference one control(giving that control multiple options). But for each option two rows are made in table B: one row with controlOptionType = "linkToCreator" and controlOptionValue = (an ID to the template it was made from*). And the other row type = "optionSelected" and value = "true"(or false).
= its a pretty complicated setup, but basically instead of set columns we are making dynamic ones by means of the type being what the column would have been called. So I couldnt link to the template with FK.
So now I need to select every control(which will have 2 controlOptions linking to it) where the one controlOptionValue value is true or false(depending on what i need) and the other controlOptionValue is an text ID that I specify.
What I think is the best way to do it is a
SELECT * FROM tableB WHERE controlOptionType = 'linkToCreator'
Then do a loop over that result set saying:
SELECT * FROM tableB WHERE tableB.controlID = (the controlID in this iterations row) AND tableB.controlValue = 'true'
But maybe thatls really inefficient, and either way I have no clue how to do that. It would be great if I could get a single query(i.e. not using stored procedures) that I specified templateID and true or false and it gave me a row result if it didn't find anything.
BTW this is for a search in our application with will need to go through TONS of rows so performance is paramount. And yes, I know the setup isnt the greatest...
Thanks :D
Like this?
SELECT * FROM tableA AS A
LEFT JOIN tableB AS ctrl1 ON (A.controlID = ctrl1.controlID AND ctrl1.controlOptionType = ? AND ctrl1.controlOptionValue = ?)
LEFT JOIN tableB AS ctrl2 ON (A.controlID = ctrl2.controlID AND ctrl2.controlOptionType = ? AND ctrl2.controlOptionValue = ?)
Try this:
SELECT *
FROM Table_A
LEFT JOIN Table_B
ON Table_A.ControlID = Table_B.ControlID
WHERE Table_A.controlOptionType = 'linkToCreator