SOPHIA MILESTONE 3- UNIT 3 CONCEPTS WITH RATIONALE

1/1/22, 3:42 AM

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Score 14/21

You passed this Milestone 14 questions were answered correctly.

7 questions were answered incorrectly.

1 In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ In the following scenario, which of the following statements would be saved to the database assuming these are all in a single transaction?

1. Update ROLLBACK 2. Insert 3. Insert 4. Delete ROLLBACK 5. Update COMMIT

UNIT 3 — MILESTONE 3

None

5

2, 3, 4, 5

1, 2, 3, 4, 5

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1/1/22, 3:42 AM

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RATIONALE In a transaction, if a ROLLBACK statement is run, all statements up to the prior COMMIT or ROLLBACK will be reverted. If a COMMIT statement is run, all statements up to the prior ROLLBACK or COMMIT will be saved.

CONCEPT COMMIT and ROLLBACK to Manage Changes 2 In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ Which of the following statements would clean the data prior to restoring the database mydatabase from backup.sql?

psql -a mydatabase < backup.sql

psql -c mydatabase < backup.sql

psql mydatabase < backup.sql

psql -d mydatabase < backup.sql

RATIONALE Common mistakes when restoring a database using the command line include, using the wrong file redirect operator, using the incorrect syntax, not using the right order of statements, or not including the command line options.

CONCEPT Restore from Backup 3 In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ Which of the following scenarios reflect the atomicity property? https://app.sophia.org/spcc/introduction-to-relational-databases/milestone_take_feedbacks/12141789

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1/1/22, 3:42 AM

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1. In the library database, there are 50 books available.

2. Billy has checked and there are 50 books.

3. Sam has checked and there are 50 books.

4. Billy has taken out 5 books.

5. The library system informs Sam of the update and Sam now checks that there are 45 books.

6. Sam checks out 10 books.

7. There are now 35 books in the library database.

1. In the flower database, there are 50 flowers available.

2. Reese has checked and there are 50 flowers.

3. Reese has attempted to take out 5 flowers.

4. While trying to take them out, there was an error in trying to dispense.

5. While checking, there are still 50 flowers available in the system.

1. A user attempts to do a product transfer between companies.

2. The quantity of the product is moved from the first company.

3. Only once the product is verified to have been deducted, the quantity is moved to the second company.

4. Verification is done and identifies that the total amounts before and after the transactions are not maintained.

5. The transaction is reverted.

1. Tiffany has updated a customer's address while on the phone with them.

2. The server restarted after Tiffany clicked on save.

3. When the server came back up, Tiffany was able to verify that the address was updated.

RATIONALE Atomicity requires that all SQL requests in a transaction should be fully completed and if not, the entire transaction should be aborted. The transaction should be viewed as a single logical unit of work that is indivisible.

CONCEPT Atomicity 4 In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ Most SQL injections are performed through this type of application that acts as an interface to the database.

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1/1/22, 3:42 AM

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Web

Text

Image

System

RATIONALE A web application is typically is used to perform SQL injections as they are meant to mimic users accessing the database.

CONCEPT Application Security 5 In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ Which of the following statements represents a correctly structured transaction?

BEGIN; ROLLBACK; UPDATE track set media_type_id = 1 where album_id = 3; DELETE FROM playlist WHERE playlist_id = 1; INSERT INTO genre (genre_id, name) VALUES (30, 'Funk' ),(31,'Classical'),(32,'Pop Rock');

BEGIN UPDATE track set media_type_id = 1 where album_id = 3 DELETE FROM playlist WHERE playlist_id = 1 INSERT INTO genre (genre_id, name) https://app.sophia.org/spcc/introduction-to-relational-databases/milestone_take_feedbacks/12141789

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1/1/22, 3:42 AM

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VALUES (30, 'Funk' ),(31,'Classical'),(32,'Pop Rock') ROLLBACK

BEGIN; UPDATE track set media_type_id = 1 where album_id = 3; DELETE FROM playlist WHERE playlist_id = 1; INSERT INTO genre (genre_id, name) VALUES (30, 'Funk' ),(31,'Classical'),(32,'Pop Rock'); ROLLBACK;

UPDATE track set media_type_id = 1 where album_id = 3; DELETE FROM playlist WHERE playlist_id = 1; INSERT INTO genre (genre_id, name) VALUES (30, 'Funk' ),(31,'Classical'),(32,'Pop Rock'); ROLLBACK;

RATIONALE Common mistakes with a transaction include missing a ; after BEGIN as well as each statement including the COMMIT or ROLLBACK statement, not having the COMMIT or ROLLBACK at the end of the statement, and not including BEGIN at the start of the statement.

CONCEPT Transactions 6 In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ Which of the following scenarios reflect the consistency property?

1. A fairly large update to the products table.

2. The update is saved to the logs.

3. The update starts to then save to the disk.

4. The system fails midway through.

5. When the system starts back up, the committed transactions that haven't been written to disk are written.

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1/1/22, 3:42 AM

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1. The product quantity starts at 200.

2. Transaction 1 runs to read the quantity of the product to be updated.

3. Transaction 2 runs in parallel to read the quantity of the product to be updated.

4. Transaction 1 updates the product quantity to reduce it by 100.

5. Transaction 2 updates the product quantity to reduce it by 5.

6. The product quantity ends at 95.

1. Transaction 1 reads a product's cost which is set at $100.

2. Transaction 1 updates the product to set the price to $90.

3. Transaction 2 reads the same product's cost and sees $100.

4. Transaction 1 commits the cost.

5. Transaction 3 reads the same product's cost and sees $90.

1. User 1 has $500 in their online account.

2. User 2 has $300 in their online account.

3. User 1 sends user 2 $100.

4. User 1 has $400 in their account.

5. User 2 has $300 in their account.

5. The transaction is reverted.

RATIONALE The consistency property ensures that a transaction takes the database from one consistent state to another consistent state. If any transaction parts violates an integrity constraint, the entire transaction should be rolled back.

CONCEPT Consistency 7 In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ Which of the following statements will grant insert permissions on the track table to all users?

GRANT INSERT ON track TO ALL;

GRANT INSERT ON track TO public;

GRANT INSERT ON public to track; https://app.sophia.org/spcc/introduction-to-relational-databases/milestone_take_feedbacks/12141789

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1/1/22, 3:42 AM

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GRANT INSERT ON 'track' TO 'public';

RATIONALE Common mistakes when granting privileges to roles include using quotes around the table or role name, not using commas between privileges, including the incorrect privileges, or not using the right syntax.

CONCEPT GRANT to Assign Privileges 8 In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ Which of the following statements would create a user named temporary_user with the password set as changeme that is valid until 2025-05-01?

CREATE USER temporary_user VALID UNTIL '2025-05-01' WITH PASSWORD 'changeme'

CREATE USER temporary_user WITH PASSWORD 'changeme' EXPIRES '2025-05-01'

CREATE USER temporary_user WITH PASSWORD changeme VALID UNTIL 2025-05-01

CREATE USER temporary_user WITH PASSWORD 'changeme' VALID UNTIL '2025-05-01'

RATIONALE Common mistakes when creating a user include adding quotes to the username, forgetting to add quotes to the password, incorrectly setting the additional parameters, or using the incorrect syntax.

CONCEPT https://app.sophia.org/spcc/introduction-to-relational-databases/milestone_take_feedbacks/12141789

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1/1/22, 3:42 AM

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CREATE USER/ROLE to Add Users 9 In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ Which of the following permissions are automatically granted to a user?

Change items in the database

Enabling extensions

All permissions need to be granted to the user or role

Any piece that touches the underlying system

RATIONALE All permissions need to be granted to the user explicitly for the user to have access. Only superusers have all permissions directly available to their account or role.

CONCEPT Superusers 10 In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ Which of the following scenarios reflects the durability property?

1. A fairly large transaction is run to import new customers.

2. The import is saved to the logs.

3. The import starts to then save to the disk.

4. The disk fails midway through the update before being committed.

5. A new disk replaces the failed disk.

6. The backup is applied and the saving of the data is run from the logs.

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1/1/22, 3:42 AM

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1. Jeff checks his user profile and sees his email address is set to jeff@gmail.com.

2. Jeff changes his email to set it to jeff@outlook.com but does not click on save yet.

3. A customer rep checks into Jeff's account and sees jeff@gmail.com.

4. Jeff clicks on save.

5. Another customer rep checks Jeff's account and sees jeff@outlook.com.

1. User 1 has $500 in their online account.

2. User 2 has $300 in their online account.

3. User 1 sends user 2 $100.

4. User 1 has $400 in their account.

5. User 2 has $300 in their account.

6. The transaction is reverted.

1. A vendor has 5 orders available.

2. A customer attempts to purchase all 5.

3. The system deducts it from the vendor and adds it to the customer.

4. The vendor now has 0 orders available.

5. The customer has 5 orders purchased.

6. The transaction is saved.

RATIONALE The durability property ensures that once a transaction is done and committed, the changes cannot be undone or lost even if there is system failure.

CONCEPT Durability 11 In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ Which of the following properties are specific to the durability property?

Data used in one transaction cannot be used in another transaction until the first transaction is completed.

If any of the transaction parts violates an integrity constraint, the entire transaction must be aborted.

A transaction should be treated as a single logical unit of work that is indivisible. https://app.sophia.org/spcc/introduction-to-relational-databases/milestone_take_feedbacks/12141789

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1/1/22, 3:42 AM

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In the event of system failure, no transactions that were done should be undone.

RATIONALE The durability property ensures that once a transaction is done and committed, the changes cannot be undone or lost even if there is a system failure.

CONCEPT ACID Properties 12 In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ Which type of backup would result in the largest storage space?

Nightly backup

Differential backup

Incremental backup

Full backup

RATIONALE Full backups are a full copy of the entire data set. Although they are the best protection, they are timeconsuming and quite large to store. Incremental backups only back up the data that has changed since the previous backup even if it's another incremental backup. These file sizes are the smallest out of the lot.

Differential backups are similar to incremental backups but it starts with a full backup and includes data since the prior full backup. At most, there are only 2 backups to restore from.

CONCEPT Backup Methods 13 In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://app.sophia.org/spcc/introduction-to-relational-databases/milestone_take_feedbacks/12141789

10/17

1/1/22, 3:42 AM

Sophia :: Welcome

https://postgres.sophia.org/ Which of the following statements would only dump the data definitions and not the data of the mydatabase to backup.sql?

pg_dump -d mydatabase > backup.sql

pg_dump mydatabase > backup.sql

pg_dump -a mydatabase > backup.sql

pg_dump -s mydatabase > backup.sql

RATIONALE Common mistakes when backing up a database using the command line include, using the wrong file redirect operator, using the incorrect syntax, not using the right order of statements or not including the command line options.

CONCEPT Create a Backup 14 In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ Which of the following cases would make the most sense to use a hash index?

SELECT * FROM customer WHERE customer_id > 10 AND customer_id < 20;

SELECT * FROM album WHERE artist_id < 5;

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1/1/22, 3:42 AM

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SELECT * FROM employee WHERE address LIKE '%i%';

SELECT * FROM track WHERE media_type_id = 1;

RATIONALE Hash indexes can only be used when we have equality comparisons. It does not do well with wild cards or any ranges.

CONCEPT Hash Index 15 In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ Which of the following sequence of statements would ensure that Jimmy has the privileges of the roles of health_department and manager?

CREATE ROLE manager NOINHERIT; CREATE ROLE health_department NOINHERIT; GRANT health_department to jimmy; GRANT manager to jimmy;

CREATE ROLE manager NOINHERIT; CREATE ROLE health_department NOINHERIT; GRANT manager to jimmy; GRANT manager to health_department;

CREATE ROLE manager NOINHERIT; CREATE ROLE health_department NOINHERIT; GRANT health_department to jimmy; GRANT manager to health_department;

CREATE ROLE manager NOINHERIT; CREATE ROLE health_department INHERIT; https://app.sophia.org/spcc/introduction-to-relational-databases/milestone_take_feedbacks/12141789

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1/1/22, 3:42 AM

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GRANT health_department to jimmy; GRANT manager to health_department;

RATIONALE Common mistakes when assigning roles include not identifying which roles have INHERIT or NOINHERIT privileges, or not ensuring that the user has all of the roles allocated to the user.

CONCEPT GRANT to Assign Users 16 In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ Which of the following operators will attempt to use a hash or b-tree index?

=

>>

&&

@>

RATIONALE By default, the b-tree index will be used if one of the following operators are used: <, <=, =, >= or >. The hash index will only be used if it is involved in a = operator. GiST indexes are focused on multiple indexing strategies being used and would be used in other operators.

CONCEPT Index Overview 17 In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ https://app.sophia.org/spcc/introduction-to-relational-databases/milestone_take_feedbacks/12141789

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1/1/22, 3:42 AM

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Which of the following statements would create a role named database_admin and gives them the ability to create databases?

CREATE ROLE database_admin CREATEROLE;

CREATE ROLE database_admin NOINHERIT;

CREATE ROLE database_admin INHERIT;

CREATE ROLE database_admin CREATEDB;

RATIONALE Common mistakes when creating roles are using quotes around the role name, not setting the correct role privileges, or not using the right syntax.

CONCEPT CREATE ROLE to Create Groups 18 In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ Which is an advantage of both the command line and the GUI?

We can use any parameters without limitation.

We can restore a remote database.

We can back up multiple databases at once.

We can encode the backup file to another format.

RATIONALE https://app.sophia.org/spcc/introduction-to-relational-databases/milestone_take_feedbacks/12141789

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1/1/22, 3:42 AM

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With the command line, you have more flexibility with all of the parameters to backup and restore the database.

You're able to pipe together commands to be able to backup and restore data into different databases and have more control. With the GUI, you have more options to select from but all of them are limited to the functionality that has been implemented. Both types do allow us to continue to restore a database or stop if there's an error.

We're also able to encode the backup files or backup the data, schema, or both using either option.

CONCEPT Backups: Command Line vs. GUI 19 In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ Which of the following cases would make the most sense to use a b-tree index?

SELECT * FROM album WHERE artist_id < 5;

SELECT * FROM customer WHERE customer_id > 10 AND customer_id < 20;

SELECT * FROM customer WHERE fax LIKE '+55%';

SELECT * FROM employee WHERE address LIKE '%i%';

RATIONALE The b-tree index makes the most sense to use when the data is even and balanced. It works best on data types like text, numbers and timestamps when we compare ranges or content that start with a value. It does not do well with wild cards at the start of a comparison or ranges.

CONCEPT B-Tree Index 20 https://app.sophia.org/spcc/introduction-to-relational-databases/milestone_take_feedbacks/12141789

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1/1/22, 3:42 AM

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In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ Which of the following scenarios reflect the isolation property?

1. A fairly large update to the products table.

2. The update is saved to the logs.

3. The update starts to then save to the disk.

4. The system fails midway through.

5. When the system starts back up, the committed transactions that haven't been written to disk are written.

1. User 1 has $500 in their online account.

2. User 2 has $300 in their online account.

3. User 1 sends user 2 $100.

4. User 1 has $400 in their account.

5. User 2 has $300 in their account.

6. The transaction is reverted.

1. Transaction 1 reads a product's cost which is set at $100.

2. Transaction 1 updates the product to set the price to $90.

3. Transaction 2 reads the same product's cost and sees $100.

4. Transaction 1 commits the cost.

5. Transaction 3 reads the same product's cost and sees $90.

1. The product quantity starts at 200.

2. Transaction 1 runs to read the quantity of the product to be updated.

3. Transaction 2 runs in parallel to read the quantity of the product to be updated.

4. Transaction 1 updates the product quantity to reduce it by 100.

5. Transaction 2 updates the product quantity to reduce it by 5.

6. The product quantity ends at 195.

RATIONALE The isolation property ensures that the data that's used in a transaction cannot be used in another transaction until the original transaction is complete with it. This is important when you have multiple users accessing and updating data in the database at the same time.

CONCEPT Isolation 21

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1/1/22, 3:42 AM

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In each milestone, you may want or need to use the database and query tool to answer some of the questions. We suggest you open the tool in another browser tab while you are working on this assessment. https://postgres.sophia.org/ Which of the following DROP INDEX statements parameters' are set by default?

DROP INDEX myindex CASCADE;

DROP INDEX IF EXISTS myindex;

DROP INDEX CONCURRENTLY myindex;

DROP INDEX myindex RESTRICT;

RATIONALE Common mistakes when it comes to dropping an index include not including the correct index name, not using the right syntax, and not using the right parameters based on the requirements. Using IF EXISTS will not throw an error if the index does not exist. CONCURRENTLY will drop the index without locking concurrent select, insert, updates and deletes. CASCADE will automatically drop objects that depend on the index. RESTRICT will refuse to drop the index if any objects depend on it. This is set by default.

CONCEPT DROP INDEX to Remove Indexes

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