Azure Data Fundamentals (DP-900) Exam Preparation：Relational data on Azure

1. 第1题，共20题

   In a relational database table, what does each row represent?

   • AThe data type of a column
   • BA single instance of an entity
   • CA link to another database
   • DA single attribute of an entity
   显示答案

   答案: B. A single instance of an entity

   Each table models a collection of entities, and each row holds one instance, such as one customer or one order.

2. 第2题，共20题

   A customer has no middle name, so the MiddleName column in their row is empty. What is this empty value called in SQL?

   • AZero
   • BNULL
   • CA default row
   • DA blank key
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   答案: B. NULL

   Every row in a table has the same columns, but some columns may have no value. An empty value is called NULL.

3. 第3题，共20题

   What is the job of a primary key in a relational table?

   • AIt uniquely identifies each row in the table
   • BIt sorts the rows by date
   • CIt encrypts the data in the table
   • DIt stores a copy of a related table
   显示答案

   答案: A. It uniquely identifies each row in the table

   Each instance of an entity gets a primary key, such as an ID, that uniquely identifies it.

4. 第4题，共20题

   An Order table has a CustomerID column that holds the ID of the customer who placed each order. What is CustomerID in the Order table?

   • AAn index
   • BA view
   • CA primary key of the Order table
   • DA foreign key
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   答案: D. A foreign key

   When one entity refers to another, the primary key of the related entity is stored as a foreign key.

5. 第5题，共20题

   What is the main purpose of normalization?

   • ATo combine all of the data into one wide table
   • BTo reduce duplicate data and enforce data integrity
   • CTo speed up nightly backups of the database
   • DTo convert relational tables into JSON documents
   显示答案

   答案: B. To reduce duplicate data and enforce data integrity

   Normalization is a schema design process that minimizes data duplication and enforces data integrity, for example by storing each customer only once.

6. 第6题，共20题

   A database refuses to save an order whose CustomerID does not match any customer in the Customer table. What is the database enforcing?

   • ANormalization
   • BAtomicity
   • CReferential integrity
   • DData masking
   显示答案

   答案: C. Referential integrity

   A relational database can enforce referential integrity, so a foreign key value must match an existing primary key in the related table.

7. 第7题，共20题

   A LineItem table identifies each row by the combination of OrderNo and ItemNo. What kind of key is this?

   • AA composite key
   • BA partition key
   • CA foreign key only
   • DA surrogate index
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   答案: A. A composite key

   A composite key uses a unique combination of more than one column, such as order number plus item number.

8. 第8题，共20题

   CREATE, ALTER, DROP and RENAME belong to which group of SQL statements?

   • AData Manipulation Language (DML)
   • BTransaction Control Language (TCL)
   • CData Definition Language (DDL)
   • DData Control Language (DCL)
   显示答案

   答案: C. Data Definition Language (DDL)

   DDL statements create, change and remove database objects such as tables and views.

9. 第9题，共20题

   A database administrator uses GRANT, DENY and REVOKE. Which group of SQL statements are these?

   • AData Query Language (DQL)
   • BData Manipulation Language (DML)
   • CData Definition Language (DDL)
   • DData Control Language (DCL)
   显示答案

   答案: D. Data Control Language (DCL)

   DCL statements manage permissions: they grant, deny or remove a user's right to perform actions.

10. 第10题，共20题

    Which SQL statement adds new rows to a table?

    • AALTER
    • BUPDATE
    • CINSERT
    • DSELECT
    显示答案

    答案: C. INSERT

    INSERT adds new rows. UPDATE changes existing rows, ALTER changes a table's structure and SELECT reads rows.

11. 第11题，共20题

    A Customer table has 1,250 rows. Someone runs UPDATE Customer SET Country = 'Canada'; with no WHERE clause. How many rows are changed?

    • ANo rows, because SQL asks for confirmation
    • BAll 1,250 rows
    • COnly rows where Country is empty
    • DOnly the first row
    显示答案

    答案: B. All 1,250 rows

    Without a WHERE clause, UPDATE changes every row in the table, and SQL does not ask "are you sure?" first.

12. 第12题，共20题

    Which SQL dialect is used by Azure SQL Database, Azure SQL Managed Instance and SQL Server?

    • ApgSQL
    • BTransact-SQL (T-SQL)
    • CCQL
    • DPL/SQL
    显示答案

    答案: B. Transact-SQL (T-SQL)

    Microsoft SQL Server and the Azure SQL services use Transact-SQL. PL/SQL is Oracle's dialect and pgSQL is PostgreSQL's.

13. 第13题，共20题

    Use the Product table above. How many rows does this query return? SELECT Name FROM Product WHERE Category = 'Tools' AND Price < 100;

    ID	Name	Price	Category
    1	Hammer	12.50	Tools
    2	Drill	89.99	Tools
    3	Tape	4.25	Supplies
    4	Gloves	9.75	Safety
    5	Ladder	149.00	Tools
    6	Vest	24.00	Safety

    • A2
    • B3
    • C6
    • D5
    显示答案

    答案: A. 2

    Both conditions must be true. Hammer (12.50) and Drill (89.99) are tools under 100, so 2 rows are returned. Ladder is a tool but costs 149.00.

14. 第14题，共20题

    Which database object is a virtual table based on a SELECT query, which you can query much like a table?

    • AA view
    • BAn index
    • CA primary key
    • DA stored procedure
    显示答案

    答案: A. A view

    A view is like a window on chosen rows from one or more tables. You can query and filter it like a table.

15. 第15题，共20题

    An app often needs to rename products. A developer saves the UPDATE logic in the database with parameters for the product ID and new name. What has the developer created?

    • AA stored procedure
    • BA view
    • CAn index
    • DA foreign key
    显示答案

    答案: A. A stored procedure

    A stored procedure holds SQL statements that run on command, and parameters let the same logic work for any product.

16. 第16题，共20题

    What is a cost of adding an index to a table?

    • AIt removes duplicate rows from the table automatically
    • BIt uses storage and must be kept up to date when data changes
    • CIt stops other users from reading the table while it exists
    • DIt makes every SELECT query on the table run more slowly
    显示答案

    答案: B. It uses storage and must be kept up to date when data changes

    Indexes speed up searches, but they take storage space and must be maintained each time the data changes.

17. 第17题，共20题

    Which Azure SQL option is an infrastructure as a service (IaaS) offering that gives you full control of the operating system and SQL Server?

    • AAzure SQL Database elastic pool
    • BAzure SQL Database
    • CSQL Server on Azure Virtual Machines
    • DAzure SQL Managed Instance
    显示答案

    答案: C. SQL Server on Azure Virtual Machines

    SQL Server on Azure VMs is IaaS. You manage the operating system, SQL Server updates, backups and maintenance yourself.

18. 第18题，共20题

    A company wants to move an on-premises SQL Server instance and all its databases to Azure with minimal app changes and near-100% compatibility, without managing virtual machines. Which option fits best?

    • AAzure Database for PostgreSQL
    • BAzure SQL Managed Instance
    • CAzure SQL Database single database
    • DSQL Server on Azure Virtual Machines
    显示答案

    答案: B. Azure SQL Managed Instance

    Azure SQL Managed Instance runs a full SQL Server instance as PaaS with near-100% compatibility, and it automates backups and patching.

19. 第19题，共20题

    A payroll database is busy at the end of each month, and a reporting database is busy in the middle of the month. Which Azure SQL Database option lets them share resources to reduce costs?

    • AA Hyperscale read replica
    • BA single database with fixed resources
    • CSQL Server on an Azure virtual machine
    • DAn elastic pool
    显示答案

    答案: D. An elastic pool

    In an elastic pool, several databases share a pool of resources. This suits databases whose needs vary over time.

20. 第20题，共20题

    A team runs a LAMP stack web app (Linux, Apache, MySQL, PHP) and wants a managed database in Azure with few app changes. Which service fits best?

    • AAzure Database for MySQL
    • BAzure Database for PostgreSQL
    • CAzure Table storage
    • DAzure SQL Managed Instance
    显示答案

    答案: A. Azure Database for MySQL

    Azure Database for MySQL is a PaaS version of MySQL Community Edition. MySQL is the leading open-source database for LAMP stack apps.

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