SQL Server Basics Quiz

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Questions and Answers

What does the query `SELECT DATEDIFF(day, '2023-01-01', '2023-01-15');` return?

14 (correct)

What is a primary advantage of using the `IDENTITY` property in SQL Server?

It automatically generates a unique number for a new row (correct)

It is used to create a default value for columns

It enforces uniqueness across multiple columns

It allows indexing on a composite key

Which statement is true about a clustered index in SQL Server?

It can only be created on primary key columns

It allows multiple clustered indexes per table

It modifies the physical storage of the data rows in the table (correct)

It requires all columns in the index to be unique

What output does the query `SELECT REPLICATE('SQL', 3);` provide?

'SQLSQLSQL' Signup and view all the answers

In SQL Server, the `WITH` keyword used in a query is primarily utilized for what purpose?

It creates a Common Table Expression (CTE) Signup and view all the answers

Which function is used in SQL Server to handle NULL values effectively?

COALESCE Signup and view all the answers

What role does the `CASE` statement serve in SQL Server?

It allows conditional logic within a query Signup and view all the answers

What occurs if a DELETE query lacks a WHERE clause in SQL Server?

All records in the table are deleted Signup and view all the answers

What does the SQL query return when using 'SELECT TOP(5) * FROM Orders ORDER BY OrderDate DESC'?

The 5 most recent orders based on OrderDate Signup and view all the answers

Which statement accurately reflects the behavior of transactions in SQL Server?

A transaction is automatically committed if no errors occur Signup and view all the answers

What does the `UNION` operator accomplish in SQL Server?

It returns all distinct rows from two or more result sets Signup and view all the answers

How can one force the SQL Server query optimizer to use a specific index?

By using the <code>INDEX</code> hint in the query Signup and view all the answers

What is the result of executing 'SELECT DISTINCT Name FROM Customers'?

Returns unique customer names Signup and view all the answers

Which characteristic is true regarding table variables in SQL Server?

Table variables are stored in memory and are faster than temporary tables Signup and view all the answers

What is the primary function of the `ROW_NUMBER()` function in SQL Server?

It assigns a unique number to each row, starting from 1 Signup and view all the answers

Study Notes

SQL Server Query Insights

DATEDIFF function: Returns the difference in days between two dates. In the given example, it calculates the days from '2023-01-01' to '2023-01-15', resulting in 14 days.
IDENTITY property: Automatically generates a unique integer for new rows in a table, often used for primary keys.
Clustered Index: Organizes data rows in a table in sorted order based on the indexed column(s) and improves retrieval performance. It can be created on any column, not just primary keys.

SQL Server String Functions

REPLICATE function: Duplicates a given string for a specified number of times. Using REPLICATE('SQL', 3) results in 'SQLSQLSQL'.
Common Table Expression (CTE): Defined using the WITH keyword, allowing for temporary result sets within a main query.

SQL Server Functions and Conditional Logic

COALESCE function: Returns the first non-NULL value from a list of expressions, useful for handling NULL values.
CASE statement: Enables conditional logic within SQL queries; it can evaluate multiple conditions and return specific results based on those evaluations.

SQL Server Data Manipulation

DELETE statement without WHERE clause: If executed without a WHERE clause, it will delete all records from the specified table.
FILESTREAM storage: Allows storage of unstructured data, such as text files, directly in SQL Server.

SQL Server Query Syntax

TOP clause: Retrieves a specified number of records; SELECT TOP(5) * FROM Orders ORDER BY OrderDate DESC returns the 5 most recent orders based on the OrderDate.
Transactions in SQL Server: Automatically committed if no errors occur, ensuring data integrity. They can be nested and are compatible with DELETE operations.

SQL Server Set Operations

UNION operator: Combines two or more result sets and returns only distinct rows from them.
INDEX hint: Forces the query optimizer to utilize a specified index, which can impact performance.

SQL Server Data Retrieval

DISTINCT keyword: Used in queries to return only unique records from a result set, as demonstrated by SELECT DISTINCT Name FROM Customers returning only unique customer names.

SQL Server Table Variables

Table variables: Stored in memory and typically offer better performance for small data sets compared to temporary tables. They support basic transactions and are limited regarding indexing capabilities.

Window Functions

ROW_NUMBER() function: Assigns a sequential integer to rows within a result set, starting from 1, often used for pagination or ranking.

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Description

Test your knowledge on SQL Server fundamentals with this quiz. You will encounter questions related to date functions, the IDENTITY property, and other essential SQL concepts. Perfect for beginners looking to strengthen their skills!