LINQ Questions and Answers

This set of SQL Server Multiple Choice Questions & Answers (MCQs) focuses on “LINQ – 1”.

1. Query alternative to the following SQL code in LINQ is ____________

SELECT TOP 10 UPPER (c1.Name)
FROM Customer c1
WHERE
   c1.Name LIKE 'A%'
   AND c1.ID NOT IN
   (
      SELECT TOP 20 c2.ID
      FROM Customer c2
      WHERE c2.Name LIKE 'A%'
      ORDER BY c2.Name
   ) 
ORDER BY c1.Name

var query =
   FROM c IN db.Customers
   WHERE c.Name.EndsWith ("A")
   orderby c.Name
   SELECT c.Name.ToUpper();
var thirdPage = query.Skip(20).Take(10);

var query =
   FROM c IN db.Customers
   WHERE c.Name.StartsWith ("65")
   orderby c.Name
   SELECT c.Name.ToUpper();
var thirdPage = query.Skip(20).Take(10);

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var query =
   FROM c IN db.Customers
   WHERE c.Name.StartsWith ("A")
   orderby c.Name
   SELECT c.Name.ToUpper();
var thirdPage = query.Skip(20).Take(10);

var query =
   FROM c IN db.Customers
   WHERE c.Name.StartsWith ("A")
   orderby c.Name
   SELECT c.Name.ToLower();
var thirdPage = query.Skip(20).Take(10);

View Answer

Answer: c
Explanation: In the case of LINQ to SQL or Entity Framework, the translation engine will convert the query into a single SQL statement optimized for the database server to which it’s connected.

2. Point out the correct statement.
a) LINQ supports flat outer joins
b) LINQ’s parameterization is inline, typesafe, and highly readable
c) LINQ queries are composable
d) All of the mentioned
View Answer

Answer: d
Explanation: We can add predicates conditionally in LINQ.

3. LINQ query to retrieve a selection of customers, each with their high-value purchases is _____________
a)

FROM c IN db.Customers
WHERE c.Address.State == "WA"
SELECT NEW
{
   c.Name,
   c.CustomerNumber,
   HighValuePurchases = c.Purchases.Where (p => p.Price > 1000)
}

FROM c IN db.Customers
WHERE c.Address.State = "WA"
SELECT NEW
{
   c.Name,
   c.CustomerNumber,
   HighValuePurchases = c.Purchases.Where (p => p.Price > 1000)
}

FROM c IN db.Customers
WHERE c.Address.State == "WA"
SELECT NEW
{
   c.Name,
   c.CustomerNumber,
   HighValuePurchases != c.Purchases.Where (p => p.Price > 1000)
}

d) All of the mentioned
View Answer

Answer: a
Explanation: HighValuePurchases, here, is a collection and because we were querying an association property, we didn’t need to join.

4. LINQ Query to list all purchases of $1000 or greater made by customers who live in Washington.
a)

FROM p IN db.Purchases
WHERE p.Customer.Address.State == "WA" || p.Customer == NULL
WHERE p.PurchaseItems.Sum (pi => pi.SaleAmount) = 1000
SELECT p

FROM p IN db.Purchases
WHERE p.Customer.Address.State == "WA" || p.Customer == NULL
WHERE p.PurchaseItems.Sum (pi => pi.SaleAmount) < 1000
SELECT p

FROM p IN db.Purchases
WHERE p.Customer.Address.State == "WA" || p.Customer == NULL
WHERE p.PurchaseItems.Sum (pi => pi.SaleAmount) > 1000
SELECT p

d) None of the mentioned
View Answer

Answer: c
Explanation: SQL will require querying across four tables (Purchase, Customer, Address and PurchaseItem).

5. Point out the wrong statement.
a) Compared to SQL, LINQ is complex, tidier, and lower-level
b) LINQ supports ad hoc join
c) Another benefit of LINQ is that you can query across relationships without having to join
d) None of the mentioned
View Answer

Answer: a
Explanation: LINQ is simpler, tidier, and higher-level

6. The following code is used will perform _________ operation in LINQ.

public bool IsValidUser(string userName, string passWord)
{
       DBNameDataContext myDB = NEW DBNameDataContext();
       List<User> users = myDB.Users.Where(u => u.Username == userName && u.Password==passWord);
       IF(users.Count>0)
       {
             RETURN TRUE;
       }
       RETURN FALSE;
}

a) update
b) select
c) insert
d) all of the mentioned
View Answer

Answer: b
Explanation: This code would be used to retrieve the data in LINQ.

7. Query alternative to the following LINQ code in SQL is ____________

FROM p IN db.Purchases
WHERE p.Customer.Address.State == "WA" || p.Customer == NULL
WHERE p.PurchaseItems.Sum (pi => pi.SaleAmount) > 1000
SELECT p

   SELECT p.*
FROM Purchase p
    LEFT OUTER JOIN 
        Customer c INNER JOIN Address a ON c.AddressID = a.ID
    ON p.CustomerID = c.ID	
WHERE
   (a.State = 'WA' || p.CustomerID IS NULL)
    AND p.ID IN
    (
        SELECT PurchaseID FROM PurchaseItem
        GROUP BY PurchaseID WHERE SUM (SaleAmount) > 1000
    )

SELECT p.*
FROM Purchase p
    LEFT OUTER JOIN 
        Customer c INNER JOIN Address a ON c.AddressID = a.ID
    ON p.CustomerID = c.ID	
WHERE
   (a.State = 'WA' || p.CustomerID IS NULL)
    AND p.ID IN
    (
        SELECT PurchaseID FROM PurchaseItem
        GROUP BY PurchaseID HAVING SUM (SaleAmount) > 1000
    )

SELECT p.*
FROM Purchase p
    LEFT OUTER JOIN 
        Customer c INNER JOIN Address a ON c.AddressID = a.ID
    ON p.CustomerID = c.ID	
WHERE
   (a.State = 'WA' || p.CustomerID IS NULL)
    AND p.ID IN
    (
        SELECT PurchaseID FROM PurchaseItem
        GROUP BY PurchaseID HAVING SUM (SaleAmount) < 1000
    )

d) None of the mentioned
View Answer

Answer: b
Explanation: Benefit of LINQ is that you can query across relationships without having to join.

8. Which of the following sample code is used to select data Using LinQ To SQL?
a)

 public bool IsValidUser(string userName, string passWord)
{
DBNameDataContext myDB = NEW DBNameDataContext();
RETURN Enumerable.Count(userResults) > 0;
}

 public bool IsValidUser(string userName, string passWord)
{
DBNameDataContext myDB = NEW DBNameDataContext();
var userResults = FROM u IN myDB.Users
                         WHERE u.Username == userName
                         && u.Password == passWord
                         SELECT u;
RETURN Enumerable.Count(userResults) > 0;
}

 public bool IsValidUser(string userName, string passWord)
{
DBNameDataContext myDB = NEW DBNameDataContext();
var userResults = FROM u IN myDB.Users
                         WHERE u.Username == userName
                         && u.Password == passWord
                         SELECT u;
RETURN Enumerable.Count(userResults) == 0;
}

d) All of the mentioned
View Answer

Answer: b
Explanation: First, when you create a new dbml file with name ‘DBName.dbml’,a corresponding DataContext class in .net is created and named something like ‘DBNameDataContext’.

9. Which of the following code snippet would traverse through all result objects ?
a)

 foreach(USER USER IN userResults)
{
    //checking the RESULT AS LIKE object
    IF(USER.Role == 'admin')
     {
         //do whatever you need
     }
}

 FOR(USER USER IN userResults)
{
    //checking the RESULT AS LIKE object
    IF(USER.Role == 'admin')
     {
         //do whatever you need
     }
}

 While(USER USER IN userResults)
{
    //checking the RESULT AS LIKE object
    IF(USER.Role == 'admin')
     {
         //do whatever you need
     }
}

d) None of the mentioned
View Answer

Answer: a
Explanation: In case, when LinQ query returns multiple results, we often need to traverse through all the result rows and process in some way and can be done very easily with a foreach loop.

10. LINQ to SQL is considered to be one of Microsoft’s _______ products.
a) ORM
b) ODBC
c) JDBC
d) SQLLIB
View Answer

Answer: a
Explanation: ORM stands for Object-Relational Mapping and it is a programming technique that contains a set of classes that map relational database entities to objects in a specific programming language.

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