Develop Reference

Join multiple tables with Select and Where clause by Lamda expression

I have 3 table like below
Table 1: Brand
+-------+---------+-------+
|Code(k)| Name | Sale | *Code - set Primary Key
+-------+---------+-------+
| AP | Apple | False |
+-------+---------+-------+
| SS | SamSung | False |
+-------+---------+-------+
| N | Nokia | False |
+-------+---------+-------+
Table 2: Category
(Code in Table 1: Brand and Brand in table Table 2: Category is same)
+-------+-------------+-------+---------+
| ID(k) | Category | Brand | Manager | *ID - set Primary Key
+-------+-------------+-------+---------+
| 1 | BasicPhone | SS | M1 |
+-------+-------------+-------+---------+
| 2 | SmartPhone | AP | M1 |
+-------+-------------+-------+---------+
| 3 | CameraPhone | SS | M1 |
+-------+-------------+-------+---------+
| 4 | Tablet | SS | M1 |
+-------+-------------+-------+---------+
| 5 | Iphone | AP | M1 |
+-------+-------------+-------+---------+
| 6 | Ipad | AP | M1 |
+-------+-------------+-------+---------+
Table 3: Product
+-------------+-------------+-------------+
| Category | CategoryDes | Description | * no Primary Key
+-------------+-------------+-------------+
| BasicPhone | NoCamera | Contact |
+-------------+-------------+-------------+
| SmartPhone | Camera | TakePhoto |
+-------------+-------------+-------------+
| CameraPhone | GoodCamera | Selfie |
+-------------+-------------+-------------+
| Tablet | BigScreen | ReadNews |
+-------------+-------------+-------------+
| Iphone | Iphone7 | Something.. |
+-------------+-------------+-------------+
| Ipad | Ipad2 | Ipad... |
+-------------+-------------+-------------+
How can I Join Table 1: Brand and Table 3: Product into Table 2: Category by Lambda expression
The result I want like this
+-----+------------+-------+---------+---------+-------+-------------+-------------+
| ID | Category | Brand | Manager | Name | Sale | CategoryDes | Description |
+-----+------------+-------+---------+---------+-------+-------------+-------------+
| 1 | BasicPhone | SS | M1 | SamSung | False | NoCamera | Contact |
+-----+------------+-------+---------+---------+-------+-------------+-------------+
| 2 | SmartPhone | AP | M1 | Apple | False | Camera | TakePhoto |
+-----+------------+-------+---------+---------+-------+-------------+-------------+
| ........... |
+-----+------------+-------+---------+---------+-------+-------------+-------------+
| ... | null | null | N | Nokia | False | null | null | *null (allowed)
+-----+------------+-------+---------+---------+-------+-------------+-------------+
Update:
I tried to Join Table 1 to Table 2
var test = db.Brand.Join(db.Category , u => u.Code, y => y.Brand,(u, y) => new { u, y });

The comment from #Holger is right, you're on the right track, just need another join. Something like this:
test = db.Brand
.Join(db.Category, b => b.Code, c => c.Brand, (b, c) => new { b, c })
.Join(db.Product, x => x.c.Category, p => p.Category, (x, p) => new { x.b, x.c, p })
Disclaimer, I didn't test this.

Check child records of a record before making status of it as false in SQL Server

I have a application with some relational tables in my SQL Server database.
In the application, whenever user deletes and records I never delete it from my database, instead I make 'status' (table column) as 'False'.
Eg: User will delete a record from tblAccounts, the records has a column 'Status' which can be either true/false. On delete action record is set to false.
Now the problem is this account may be referred in other transactions. If it is used in other tables then it should not allow user to delete (make it false).
If I allow user to delete the record physically from table, it will throw foreign key error but in this scenario (making it false) how can I check the child rows without deleting and prompt the User.
I can do it by a select query on each table but that will be slow down my application.
Is there any other way/idea to achieve it?

I can do it by a select query on each table but that will be slow down
my application.
Is there any other way/idea to achieve it?
No there is not. You can do the automation with either a CHECK constraint that calls a function or with a TRIGGER, but in that code a SELECT statement against the other tables will have to be performed. There is no way around it.

You could do it using a foreign key, the trick here is to make both columns (AccountID and Status) Primary in tblAccounts. Then in the transaction table, you create a foreign key to both (AccountID and Status) with cascade on UPDATE/Delete. This means, if you ever change/delete an account id or its status from tblAccounts, the changes will be applied on all foreign keys as well.
Here is an example :
CREATE TABLE tblAccounts(
ID INT,
AccountID INT NOT NULL,
[Status] BIT NOT NULL
)
ALTER TABLE tblAccounts
ADD PRIMARY KEY (AccountID, [Status])
CREATE TABLE tblTransactions(
[ID] INT,
[TransID] INT NOT NULL PRIMARY KEY,
[AcctID] INT NOT NULL,
[Status] BIT NOT NULL
)
ALTER TABLE tblTransactions
ADD FOREIGN KEY (AcctID,[Status]) REFERENCES tblAccounts(AccountID, [Status])
ON UPDATE CASCADE
ON DELETE CASCADE
INSERT INTO tblAccounts (ID, AccountID, [Status])
VALUES
(1,1000,1),
(2,1100,1),
(3,1200,1),
(4,1300,1)
INSERT INTO tblTransactions(ID, TransID, AcctID,[Status])
VALUES
(1,5000,1000,1),
(2,3258,1300,1),
(3,5852,1000,1),
(4,9631,1100,1),
(5,1870,1200,1)
tblAccounts
| ID | AccountID | Status |
|----|-----------|--------|
| 1 | 1000 | true |
| 2 | 1100 | true |
| 3 | 1200 | true |
| 4 | 1300 | true |
tblTransactions
| ID | TransID | AcctID | Status |
|----|---------|--------|--------|
| 1 | 5000 | 1000 | true |
| 2 | 3258 | 1300 | true |
| 3 | 5852 | 1000 | true |
| 4 | 9631 | 1100 | true |
| 5 | 1870 | 1200 | true |
Let's change the status of AccountID 1100 to false
UPDATE tblAccounts
SET
[Status] = 0
WHERE
AccountID = 1100
Check tblAccount
| ID | AccountID | Status |
|----|-----------|--------|
| 1 | 1000 | true |
| 2 | 1100 | false|
| 3 | 1200 | true |
| 4 | 1300 | true |
Check tblTransactions
| ID | TransID | AcctID | Status |
|----|---------|--------|--------|
| 1 | 5000 | 1000 | true |
| 2 | 3258 | 1300 | true |
| 3 | 5852 | 1000 | true |
| 4 | 9631 | 1100 | false|
| 5 | 1870 | 1200 | true |

MSSQL Query omitting specific row value?

I have the following query to retrieve the customer sales report based on customer ID. It works, but how can I omit the customer name being duplicated?
select Cu.CustomerName, Cu.City, pd.pname,
Cs.qty, Cs.totalAmount, Cs.payed, Cs.credit, Cs.CreditEndDate
from Customer Cu
inner join CreditSales Cs on Cu.ID=Cs.CustomerID
left join Product pd on pd.pid=Cs.pid
where Cu.ID=6
order by Cu.CustomerName
The result is:
+--------+-------+---------------+----+----------+----------+----------+------------+
| Halima | Jimma | Mouse | 1 | 345.00 | 345.00 | 0.00 | 2015-08-29 |
| Halima | Jimma | Mobile | 10 | 92000.00 | 40000.00 | 52000.00 | 2015-08-23 |
| Halima | Jimma | Iphone | 2 | 13800.00 | 6500.00 | 7300.00 | 2015-08-28 |
| Halima | Jimma | Tape Recorder | 10 | 5175.00 | 4000.00 | 1175.00 | 2015-10-30 |
+--------+-------+---------------+----+----------+----------+----------+------------+
But I need like this:
+--------+-------+---------------+----+----------+----------+----------+------------+
| Halima | Jimma | Mouse | 1 | 345.00 | 345.00 | 0.00 | 2015-08-29 |
| | Jimma | Mobile | 10 | 92000.00 | 40000.00 | 52000.00 | 2015-08-23 |
| | Jimma | Iphone | 2 | 13800.00 | 6500.00 | 7300.00 | 2015-08-28 |
| | Jimma | Tape Recorder | 10 | 5175.00 | 4000.00 | 1175.00 | 2015-10-30 |
+--------+-------+---------------+----+----------+----------+----------+------------+
That means the customer name should displayed only one instance.
Any help? Thanks in Advance.

Based on Milen Pavlov response, you can try this:
SELECT CASE WHEN ROW_NUMBER() over (partition by [CustomerName] order by [CustomerName]) = 1 THEN [CustomerName] ELSE '' END
FROM Customer
ORDER BY [CustomerName]

This could do the job (I need you have to add an ordering in the over() clause):
select case when a.rn > 1 then '' else a.CustomerName end as CustomerName, a.City, a.pname, a.qty, a.totalAmount, a.payed, a.credit, a.CreditEndDate
from
(
select Cu.CustomerName, Cu.City, pd.pname,
Cs.qty, Cs.totalAmount, Cs.payed, Cs.credit, Cs.CreditEndDate, ROW_NUMBER() over (partition by Cu.CustomerName order by Cs.CreditEndDate) as rn
from Customer Cu
inner join CreditSales Cs on Cu.ID=Cs.CustomerID
left join Product pd on pd.pid=Cs.pid
where Cu.ID=6
) a
order by a.CustomerName

don't think it's a job for SQL but if you insists you can create two tables the first one with all the rows and columns and than delete the first row, and the other table with the first row and just make a left join and make the join on all the fields.

Join Tables MySQL

I have multiple tables and made 2 sub-selects (UserRecord,CustomerRecord) that i would like to merge into 1 table
UserRecord
========================
| RecordID | UserName |
========================
| 1 | Sara |
| 1 | Tom |
| 2 | Sara |
| 2 | Kurt |
| 3 | Fre |
========================
Table: CustomerRecord
============================
| RecordID | CustomerName |
============================
| 1 | Jef |
| 2 | Alex |
| 2 | Peter |
============================
Table: This should be the result
=======================================
| RecordID | UserName | CustomerName |
=======================================
| 1 | Sara | - |
| 1 | Tom | - |
| 1 | - | Jef |
| 2 | Sara | - |
| 2 | Kurt | - |
| 2 | - | Alex |
| 2 | - | Peter |
| 3 | Fre | - |
=======================================
- = null
I tried with left, right, left outer, right outer ... join on the 2 tables but i don't get what i would like.
SELECT *
FROM UserRecord AS ur
INNER JOIN CustomerRecord AS cr ON ur.RecordID = cr.RecordID;

What you want is not a join, but a UNION:
SELECT RecordID, UserName, NULL AS CustomerName FROM UserRecord
UNION
SELECT RecordID, NULL AS UserName, CustomerName FROM CustomerRecord
... which just appends records from the two tables.
I'd just add that the order will not be the one you have shown in your expected result. If order is important then you should SELECT from this UNION and add an explicit ORDER BY clause on this outer select. Something like:
SELECT * FROM (
SELECT RecordID, UserName, NULL AS CustomerName FROM UserRecord
UNION
SELECT RecordID, NULL AS UserName, CustomerName FROM CustomerRecord
) ORDER BY RecordID, UserName, CustomerName

You can use a simple union
select recordid, username, null as customername from userrecord
union
select recordid, null, customername from customerrecord

Gridview and Select query

I am working with gridview and tables, I am using c# and asp.net. Assuming I have 2 tables, lets just name it Profiles and Info.
In table profiles let's say I have fields with p_Id, FirstName, LastName and in Transaction I have I_Id, childsID, fathersID, mothersID.
This is what my tables looks like:
Profile
| p_Id | FirstName | LastName |
| 1 | Jack | Cole |
| 2 | Cynthia | Cole |
| 3 | Robert | Cole |
Info
| I_Id | childsID | fathersID | mothersID |
| 1 | 1 | 3 | 2 |
Now in my gridview I have to display FirstName, LastName, Father and Mother. But I need to display their names not their ID's.
For now my gridview looks like this:
First Name | Last Name | Father| Mother |
Jack | Cole | 3 | 2 |
what I want is like this:
First Name | Last Name | Father | Mother |
Jack | Cole | Robert Cole | Cynthia Cole |

try this
select p.firstName, p.LastName
, (select sp.FirstName+' '+sp.Lastname FROM profile sp WHERE sp.p_id=i.fathersid) as father
, (select sp.FirstName+' '+sp.Lastname FROM profile sp WHERE sp.p_id=i.mothersid) as mother
from info i
inner join profile p ON (p.p_id=i.childsID)