Table-level permissions in PostgreSQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to grant SELECT permission on the table 'employees' to user 'john'.

PostgreSQL

GRANT [1] ON employees TO john;

Drag options to blanks, or click blank then click option'

ADELETE

BINSERT

CUPDATE

DSELECT

Attempts:

3 left

💡 Hint

Common Mistakes

Using INSERT instead of SELECT

Using UPDATE or DELETE which are for modifying data

The SELECT permission allows the user to read data from the table.

2fill in blank

medium

Complete the code to revoke INSERT permission on the table 'products' from user 'alice'.

PostgreSQL

REVOKE [1] ON products FROM alice;

Drag options to blanks, or click blank then click option'

AINSERT

BSELECT

CUPDATE

DDELETE

Attempts:

3 left

💡 Hint

Common Mistakes

Revoking SELECT instead of INSERT

Confusing UPDATE with INSERT

The INSERT permission allows adding new rows. Revoking it stops the user from inserting data.

3fill in blank

hard

Fix the error in the code to grant UPDATE permission on 'orders' to user 'mike'.

PostgreSQL

GRANT [1] ON orders TO mike;

Drag options to blanks, or click blank then click option'

AUPDATE;

BUPDATE

CUPDATE ON

DUPDATE TO

Attempts:

3 left

💡 Hint

Common Mistakes

Missing semicolon at the end

Adding extra keywords like ON or TO incorrectly

The statement must end with a semicolon ; to be valid SQL.

4fill in blank

hard

Fill both blanks to grant DELETE and SELECT permissions on 'customers' to user 'emma'.

PostgreSQL

GRANT [1], [2] ON customers TO emma;

Drag options to blanks, or click blank then click option'

ADELETE

BSELECT

CINSERT

DUPDATE

Attempts:

3 left

💡 Hint

Common Mistakes

Using INSERT or UPDATE instead of DELETE or SELECT

Forgetting the comma between permissions

To grant multiple permissions, list them separated by commas. Here, DELETE and SELECT are correct.

5fill in blank

hard

Fill all three blanks to revoke SELECT and UPDATE permissions on 'inventory' from user 'dave'.

PostgreSQL

REVOKE [1], [2] ON inventory FROM [3];

Drag options to blanks, or click blank then click option'

ASELECT

BUPDATE

Cdave

Dalice

Attempts:

3 left

💡 Hint

Common Mistakes

Revoking wrong permissions

Using wrong username in the statement

We revoke SELECT and UPDATE permissions from user 'dave'.

Practice

1. What does the GRANT SELECT ON table_name TO user_name; command do in PostgreSQL?

easy

A. Removes all permissions from the user on the specified table.

B. Allows the user to delete data from the specified table.

C. Creates a new table with the given name.

D. Allows the user to read data from the specified table.

Solution

1. Step 1: Understand the GRANT command

   The GRANT command is used to give specific permissions to users on database objects like tables.

2. Step 2: Identify the permission type SELECT

   SELECT permission allows reading data from the table but not modifying it.

3. Final Answer:

   Allows the user to read data from the specified table. -> Option D

4. Quick Check:

   GRANT SELECT = read permission [OK]

Hint: GRANT SELECT means read access only [OK]

Common Mistakes:

• Confusing SELECT with DELETE permission
• Thinking GRANT creates tables
• Mixing GRANT with REVOKE commands

2. Which of the following is the correct syntax to revoke INSERT permission on a table named employees from user john?

easy

A. REVOKE INSERT TO john ON employees;

B. REVOKE ON employees INSERT FROM john;

C. REVOKE INSERT ON employees FROM john;

D. REVOKE INSERT FROM john ON employees;

Solution

1. Step 1: Recall REVOKE syntax

   The correct syntax is REVOKE permission ON table FROM user;

2. Step 2: Match syntax with options

   REVOKE INSERT ON employees FROM john; matches the correct order: REVOKE INSERT ON employees FROM john;

3. Final Answer:

   REVOKE INSERT ON employees FROM john; -> Option C

4. Quick Check:

   REVOKE permission ON table FROM user [OK]

Hint: REVOKE syntax: REVOKE permission ON table FROM user [OK]

Common Mistakes:

• Swapping ON and FROM keywords
• Using TO instead of FROM
• Incorrect order of clauses

3. Given the commands:

GRANT SELECT ON orders TO alice;
GRANT INSERT ON orders TO bob;
REVOKE SELECT ON orders FROM alice;

Which of the following is true about user permissions on the orders table?

medium

A. Alice cannot read data; Bob can insert data.

B. Alice can read and insert data; Bob can only insert data.

C. Alice can read data; Bob cannot insert data.

D. Both Alice and Bob have no permissions on the table.

Solution

1. Step 1: Analyze granted permissions

   Alice was granted SELECT (read) permission, Bob was granted INSERT permission.

2. Step 2: Analyze revoked permissions

   Alice's SELECT permission was revoked, so she no longer can read data.

3. Final Answer:

   Alice cannot read data; Bob can insert data. -> Option A

4. Quick Check:

   Revoked SELECT removes read access [OK]

Hint: Revoking removes permission even if previously granted [OK]

Common Mistakes:

• Assuming revoked permission still applies
• Confusing INSERT with SELECT
• Thinking REVOKE affects other users

4. Consider this command:

GRANT UPDATE ON customers TO ;

What is the error in this command?

medium

A. Missing user name after TO keyword.

B. UPDATE is not a valid permission.

C. Table name is missing after ON keyword.

D. GRANT cannot be used for UPDATE permission.

Solution

1. Step 1: Check syntax completeness

   The command ends with TO but does not specify a user or role name.

2. Step 2: Validate permission and table name

   UPDATE is a valid permission and customers is the table name, so those parts are correct.

3. Final Answer:

   Missing user name after TO keyword. -> Option A

4. Quick Check:

   GRANT requires user after TO [OK]

Hint: Always specify user after TO in GRANT [OK]

Common Mistakes:

• Leaving user name blank after TO
• Confusing permission names
• Omitting table name

5. You want to allow user carol to read and insert data into the products table but prevent her from deleting or updating any data. Which commands should you use?

hard

A. GRANT ALL ON products TO carol;
REVOKE DELETE, UPDATE ON products FROM carol;

B. GRANT SELECT, INSERT ON products TO carol;
REVOKE DELETE, UPDATE ON products FROM carol;

C. GRANT SELECT, INSERT, DELETE ON products TO carol;

D. GRANT SELECT ON products TO carol;
GRANT INSERT ON products TO carol;

Solution

1. Step 1: Grant only SELECT and INSERT permissions

   To allow reading and inserting, grant SELECT and INSERT on products to carol.

2. Step 2: Revoke DELETE and UPDATE permissions

   To prevent deleting or updating, explicitly revoke DELETE and UPDATE permissions if previously granted.

3. Final Answer:

   GRANT SELECT, INSERT ON products TO carol; REVOKE DELETE, UPDATE ON products FROM carol; -> Option B

4. Quick Check:

   Grant needed permissions, revoke unwanted ones [OK]

Hint: Grant needed permissions, revoke unwanted explicitly [OK]

Common Mistakes:

• Granting ALL permissions instead of specific ones
• Not revoking unwanted permissions
• Granting DELETE or UPDATE by mistake