Join and batch update in LINQ to SQL - linq

Can something like this be written in LINQ to SQL:
UPDATE Table1
SET CustomerName = t2.Name
FROM Table1 t1 JOIN Table2 t2
ON t1.TableID = t2.TableID


var result = from t1 in context.Table1
join t2 in context.Table2 on t1.TableID = t2.TableID
select new {t1, t2};
result.ToList().ForEach(i => i.t1.CustomerName = i.t2.Name);
context.SubmitChanges();

Related

Oracle Hierarchical queries: Translate START WITH ... CONNECT BY PRIOR into 'Recursive Subquery Factoring'

How would the following START WITH / CONNECT BY hierarchical query look like when translated into a RECURSIVE SUBQUERY FACTORING hierarchical query with WITH clause:
SELECT t1.id
FROM table1 t1, table2 t2
WHERE t1.version_id = t2.id
AND t1.baseline_date = TRIM (TO_DATE ('2015-05-26', 'yyyy-mm-dd'))
AND t2.entry_date = t1.baseline_date
START WITH t1.id IN (SELECT id
FROM table1
WHERE parent_id = 101015)
CONNECT BY PRIOR t1.id = t1.parent_id
ORDER SIBLINGS BY t1.child_index;

I think you want:
WITH rsqfc (id, child_index, baseline_date) AS (
SELECT t1.id,
t1.child_index,
t1.baseline_date
FROM table1 t1
INNER JOIN table2 t2
ON ( t1.version_id = t2.id
AND t2.entry_date = t1.baseline_date )
WHERE t1.parent_id = 101015
UNION ALL
SELECT t1.id,
t1.child_index,
t1.baseline_date
FROM rsqfc r
INNER JOIN table1 t1
ON (r.id = t1.parent_id)
INNER JOIN table2 t2
ON ( t1.version_id = t2.id
AND t2.entry_date = t1.baseline_date )
)
SEARCH DEPTH FIRST BY child_index SET order_id
SELECT id
FROM rsqfc
WHERE baseline_date = DATE '2015-05-26';
However, without sample data it is difficult to be sure.

SQL Update with Join and Sub Query

I have the following queries and have trouble putting them together:
DECLARE #Value1 INT = 3
DECLARE #Value2 INT = 6
UPDATE TableA SET
Column1 = B.NewValue,
FROM TableA A INNER JOIN TableB B ON A.NumberId = B.NumberId AND
AND A.Type = #Value1
UPDATE TableA SET
Column2 = B.NewValue,
FROM TableA A INNER JOIN TableB B ON A.NumberId = B.NumberId AND
AND A.Type = #Value2
My goal is to have one query with a join that updates the columns depending on the values in the join.
This I just an example (in my case there are more columns and therefore more queries) but overall I want to have as few queries as possible (in this example: one query instead of two)
DECLARE #Value1 INT = 3
DECLARE #Value2 INT = 6
UPDATE TableA SET
Column1 = B.NewValue, --if the join joins on #Value1
Column2 = B.NewValue, --if the join joins on #Value2
FROM TableA A INNER JOIN TableB B ON A.NumberId = B.NumberId AND
AND A.Type = B.#Value1/#Value2
Is this possible (using a sub query for example)?

You can try using CASE EXPRESSION
UPDATE TableA SET
Column1 = CASE WHEN A.Type = #Value1 THEN B.NewValue
ELSE A.Column1 END,
Column2 = CASE WHEN A.Type = #Value2 THEN B.NewValue
ELSE A.Column2 END
FROM TableA A INNER JOIN TableB B ON A.NumberId = B.NumberId AND
AND A.Type IN (#Value1, #Value2)

How do you write an INNER JOIN with an "OR" in Linq

I am trying to write a Linq query to generate the following SQL
SELECT
[t1].[Id], [t2].[value3]
FROM
[Table1] AS [t1]
INNER JOIN
[Table2] AS [t2] ON [t1].[Id] = [t2].[value1]
OR [t1].[Id] = [t2].[value2]
I have seen lots of examples for how to do multiple joins, but none for how to do this type of "one or the other" join.

var result = from t1 in context.Table1
from t2 in context.Table2
where (t1.Id == t2.value1 || t1.Id == t2.value2)
select new
{
t1.Id,
t2.value3
};

INNER JOIN
var query =
from t1 in context.Table1
from t2 in context.Table2.Where(t2 => t1.Id == t2.value1 || t1.Id == t2.value2)
select new
{
t1.Id,
t2.value3
};
LEFT JOIN
var query =
from t1 in context.Table1
from t2 in context.Table2.Where(t2 => t1.Id == t2.value1 || t1.Id == t2.value2)
.DefaultIfEmpty()
select new
{
t1.Id,
t2.value3
};

Want to change SQL query to LINQ

I want to change the below simple SQL query into LINQ , how do I change it ?
select * from table1 where isPaid = 'true' and Id in (select Id from table2 where EmployeeId = 12)
similar to this ?
from pa in db.PaymentAdvices
where pa.IsPaid == true
orderby pa.PaidDate descending
select pa;

Here code linq to sql:
from t1 in table1
join t2 in table2 on t1.Id equals t2.Id
where t2.EmployeeId = 12
select t1
Hope usefull!

if the field isPaid has datatype is Boolean:
from t1 in table1
join t2 in table2 on t1.Id equals t2.Id
where t2.EmployeeId = 12 and t1.isPaid == true
select t1
if the field isPaid has datatype is String:
from t1 in table1
join t2 in table2 on t1.Id equals t2.Id
where t2.EmployeeId = 12 and t1.isPaid.Equals("true")
select t1

Linq and foreign key Lookup tables with integer keys

I have a database where the tables are:
Table1:
Table1Id int
Table2:
Table2Id int
ForeignKeyToTable1 int
LookupTable:
Table2Id
Table3Id
Table3:
Table3Id int
Table3Field varchar
I want to:
select table1.* from table1
inner join table2 on table1.Table1Id = ForeignKeyToTable1
inner join LookupTable on LookupTable.Table2Id = table2.Table2Id
inner join Table3 on table3.Table3Id = LookupTable.Table3Id
where table3.Table3Field ='qwerty'
How can this be achieved in Linq?

var query =
from table1 in db.Table1
join table2 in db.Table2 on new { Table1Id = table1.Table1Id } equals new { Table1Id = table2.ForeignKeyToTable1 }
join lookuptable in db.LookupTable on table2.Table2Id equals lookuptable.Table2Id
join table3 in db.Table3 on lookuptable.Table3Id equals table3.Table3Id
where
table3.Table3Field == "qwerty"
select new {
table1.Table1Id
};

I believe something like this will go
var query = from t1 in context.Table1
join t2 in context.Table2
on t1.Table1Id equals t2.ForeignKeyToTable1
join lt in context.LookupTable
on t2.Table2Id equals lt.Table2Id
join t3 in context.Table3
on lt.Table3Id equals t3.Table3Id
where t3.Table3Field == "qwerty"
select t1;

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