I'm struggling with a join/where clause with what is a rather simple sql select statement.
I am trying to retrieve a list of product information from tb1 with the where condition behind situated in tbl2 but this must be joined by three different columns.
so the SQL would look something along the lines of:
SELECT tb1.*
FROM tb2 INNER JOIN
tb1 ON tb2.Col1 = tb1. Col1 AND tb2.Col2 = tb1. Col2 AND
tb2.Col3 = tb1.Col3
WHERE (tb2.Col1 = col1) AND (tb2.Col2 = col2) AND (tb2.Col4 = string)
ColX is the main where clause with the string to be passed in as parameter; all other columns are within the contexts.
How do you implement multiple joins with a where clause?
And shoves in the right direction, muchly appreciated.
To join on multiple field in LINQ, you have to create a new anonymous type containing the columns you want to compare and then use that anonymous type in the join:
var results = from t1 in context.tb1
join t2 in context.tb2
on new { t1.Col1, t1.Col2, t1.Col3 } equals
new { t2.Col1, t2.Col2, t2.Col3 }
where t2.Col1 == col1 && t2.Col2 == col2 && t2.Col4 == someString
select t1;
And here is the equivalent Lambda Syntax:
var results = context.tb1.Join(
context.tb2,
t1 => new { t1.Col1, t1.Col2, t1.Col3 },
t2 => new { t2.Col1, t2.Col2, t2.Col3 },
(t1, t2) => new { t1, t2 })
.Where(o => o.t2.Col1 == col1
&& o.t2.Col2 == col2
&& o.t2.Col4 == someString)
.Select(o => o.t1);
As you can see, in the case of joins, query syntax usually produces an easier to read statement.
You can also include the WHERE clause in lamda syntax in the reference to the table you're joining on.
var query = from pt in dc.ProjectTasks
join ttab in dc.TimeTaskAssigns on pt.Id equals ttab.ProjectTaskId
join ttb2 in dc.CMS_TAT_TIMEs.Where(a => a.WIP_STATUS == 'B') on ttab.CmsTimeUno equals ttb2.TIME_UNO
select pt;
Seems obvious now, doesn't it? It took me a long time to find that solution.
Also you can group result and use subquery
var innerGroupJoinQuery2 =
from category in categories
join prod in products on category.ID equals prod.CategoryID into prodGroup
from prod2 in prodGroup
where prod2.UnitPrice > 2.50M
select prod2;
ref.: join clause (C# Reference)
Related
I have a table with the following fields:
ID, VALUES, VARIAB
Im trying to SUM the field VALUES, but it needs to be grouped by ID.
And the Subselect doesnt accept multiple lines. (When i use it with just 1 ID, works fine).
BEGIN
UPDATE TBL2
SET SOMA =
(SELECT SUM(x.VALUES)
FROM TBL3 x INNER JOIN TBL2 y
ON y.ID = x.ID
WHERE y.ID = x.ID AND X.VARIAB = 1
GROUP BY x.ID
);
END;
Im using ORACLE DB, if anyone comment this ill be very gratefull.
Sorry for my english flaws.
To update multiple records at once and/or do an upsert, use MERGE statement like this :
MERGE INTO TBL2 T2 USING (
SELECT x.id,SUM(x.VALUES) total
FROM TBL3 x
WHERE x.VARIAB = 1
GROUP BY x.ID
) T3 ON (T2.ID = T3.ID)
WHEN MATCHED THEN UPDATE
SET T2.SOMA = T3.TOTAL
The issue is that your update statement isn't correlated - ie. your subquery has no reference to the table being updated.
You could change it to:
update tbl2 t2
set soma = (select sum(t3.values)
from tbl3 t3
where t2.id = t3.id
and t3.variab = 1);
I'm trying to make a query that have a lot of subquerys (4 subquerys), but for the subquerys I need to take a value of the query, can anyone help me? This is the query:
SELECT DISTINCT tab1.value1,
ISNULL((SELECT SUM(tab2.quantity) FROM tab2 INNER JOIN tab3 ON tab2.id_tab2 = tab3.id_tab2 INNER JOIN tab4 ON tab3.id_tab3 = tab4.id_tab3 WHERE tab4.value = "value1"), 0) AS v1,
ISNULL((SELECT SUM(tab2.quantity) FROM tab2 INNER JOIN tab3 ON tab2.id_tab2 = tab3.id_tab2 INNER JOIN tab4 ON tab3.id_tab3 = tab4.id_tab3 WHERE tab4.value = "value2"), 0) AS v2
What I need to do is that in the subquerys, make an INNER JOIN with that value1 the subquery make the adding but just with the values that are of the value1, because right now the subquery make the add of all the values located in the table that are equal with "value1" or "value2", I have tryed to make a subquery like these:
ISNULL((SELECT SUM(tab2.quantity) FROM tab2 INNER JOIN tab3 ON tab2.id_tab2 = tab3.id_tab2 INNER JOIN tab4 ON tab3.id_tab3 = tab4.id_tab3 INNER JOIN tab5 ON tab2.id_tab5 = tab5.id_tab5 INNER JOIN tab1 ON tab5.id_tab1 = tab1.id_tab1 INNER JOIN tab1 ON tab1.value1 = tab1.value1 WHERE tab4.value = "value1"), 0) AS v1
But obviously it didn't function, I also have tried to use an allias for the value1 but it says that it doesn't exist, anyone have an idea?
Im going to take a stab at it... It looks like you are trying to join the four tables by _id and aggregate a sum based on the child table's (tab4) value.
In the below example I used three tables, but the idea is the same. If this doesnt meet your needs perhaps you can repurpose this example to clearly define your requirements:
declare #tab1 table (i int primary key, value varchar(10));
insert into #tab1
select 1, 'one' union all select 2, 'two'
declare #tab2 table (i int primary key, quantity varchar(10));
insert into #tab2
select 1, 10 union all
select 2, 20
declare #tab3 table (i int primary key, value varchar(10));
insert into #tab3
select 1, 'value1' union all
select 2, 'value2'
select t1.value,
sum(case when t3.value = 'value1' then t2.quantity else 0 end),
sum(case when t3.value = 'value2' then t2.quantity else 0 end)
from #tab1 t1
join #tab2 t2 on t1.i = t2.i
join #tab3 t3 on t2.i = t3.i
group
by t1.value;
I have two tables, T1 and T2 with same set of columns. I need to issue a query which will return me value of columns from either table whichever is not null. If both columns are null return null as the value of that column.
The columns are c1,c2,c3,cond1.
I issued the following query. The problem is that if one subquery fails the whole query fails. Somebody please help me. Probably there is another simple way.
SELECT NVL(T1.c1, T2.c1) c1,NVL(T1.c2, T2.c2) c2,NVL(T1.c3, T2.c3) c3
FROM (SELECT c1,c2,c3
FROM T1
WHERE cond1 = 'T10') T1
,(SELECT c1,c2,c3
FROM T2
WHERE cond1 = 'T200') T2 ;
You need something like this:
SELECT NVL((SELECT T1.c1
FROM T1
WHERE T1.c2 = 'T10'),
(SELECT T2.c1
FROM T2
WHERE T2.c2 = 'T200')) AS c1
FROM dual
Or you may prefer a full outer join:
SELECT NVL(T1.c1, T2.c1) AS c1
FROM T1 FULL OUTER JOIN T2 ON 1=1
WHERE T1.c2 = 'T10'
AND T2.c2 = 'T200'
Your result is logical. If the first table is null no combination of values will exist in the natural join.
EDIT. After some new requirements we can use a hack to get the row. Lets get all three possibilities, T1, T2 or all nulls and select the first one:
SELECT *
FROM ( (SELECT T1.*
FROM T1
WHERE T1.c2 = 'T10')
UNION ALL
(SELECT T2.*
FROM T2
WHERE T2.c2 = 'T200')
UNION ALL
(SELECT T2.*
FROM dual
LEFT JOIN T1 ON 1 = 0 ) )
WHERE ROWNUM = 1
I know we can get distinct on one column using following query:
I know we can get distinct on one column using following query:
SELECT *
FROM (SELECT A, B, C,
ROW_NUMBER() OVER (PARTITION BY B ORDER BY A) AS RowNumber
FROM MyTable
WHERE B LIKE 'FOO%') AS a
WHERE a.RowNumber = 1
I have used similar sql query in my case where i am joining multiple tables but my project is in mvc4 and i need linq to entity equivalent of the same. Here is my code:
select * from
(
select fp.URN_No,
ROW_NUMBER() OVER
(PARTITION BY pdh.ChangedOn ORDER BY fp.CreatedOn)
as num,
fp.CreatedOn, pdh.FarmersName, pdh.ChangedOn, cdh.Address1, cdh.State, ich.TypeOfCertificate, ich.IdentityNumber, bdh.bankType, bdh.bankName,
pidh.DistrictId, pidh.PacsRegistrationNumber, idh.IncomeLevel, idh.GrossAnnualIncome
from MST_FarmerProfile as fp inner join PersonalDetailsHistories as pdh on fp.personDetails_Id = pdh.PersonalDetails_Id
inner join ContactDetailsHistories as cdh on fp.contactDetails_Id = cdh.ContactDetails_Id
inner join IdentityCertificateHistories as ich on fp.IdentityCertificate_Id = ich.IdentityCertificate_Id
inner join BankDetailsHistories as bdh on fp.BankDetails_Id = bdh.BankDetails_Id
left join PacInsuranceDataHistories as pidh on fp.PacsInsuranceData_Id = pidh.PacsInsuranceData_Id
left join IncomeDetailsHistories as idh on fp.IncomeDetails_Id = idh.IncomeDetails_Id
where URN_No in(
select distinct MST_FarmerProfile_URN_No from PersonalDetailsHistories where MST_FarmerProfile_URN_No in(
select URN_No from MST_FarmerProfile where (CreatedOn>=#fromDate and CreatedOn<= #toDate and Status='Active')))
)a where a.num=1
Use this linq query after getting result from sql. p.ID is be your desire distinct column name
List<Person> distinctRecords = YourResultList
.GroupBy(p => new { p.ID})
.Select(g => g.First())
.ToList();
How can I write the below t-sql in Linq?
select (select COUNT(col1) FROM t2 WHERE col2 = t1.col2 and col1 = t1.col1) as total,
t1.col1,t1.col2...................
from t1
var res = from t1 in context.t1s
select new
{
total = context.t2s.Where(t2=> t2.col1 == t1.col1 && t2.col2 == t1.col2).Count(),
t1.col1,
t1.col2,
};
Edit:
And if you have your FK-relations set up correctly in the database and your DBML you can use the simpler version below
var res = from t1 in context.t1s
select new
{
total = t1.t2s.Count(),
t1.col1,
t1.col2,
};
Try using LinqPad. It is great for translating between SQL and LINQ queries.
http://www.linqpad.net/