TYPE command for key type check in Redis - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check the type of the key 'user:1'.

Redis

TYPE [1]

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

Auser

Buser1

C1

Duser:1

Attempts:

3 left

💡 Hint

Common Mistakes

Using a key name without the colon ':'

Using only part of the key name

Adding quotes around the key name

The TYPE command requires the exact key name to check its type. Here, the key is 'user:1'.

2fill in blank

medium

Complete the command to check the type of the key stored in variable 'keyName'.

Redis

TYPE [1]

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

AkeyName

B$keyName

C"keyName"

Dkeyname

Attempts:

3 left

💡 Hint

Common Mistakes

Adding quotes around the key name

Using shell variable syntax like $keyName

Changing the case of the key name

In Redis CLI, you pass the key name directly without quotes or variable symbols.

3fill in blank

hard

Fix the error in the command to check the type of key 'session123'.

Redis

TYPE [1]

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

A'session123'

B$session123

Csession123

D"session123"

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around the key name

Using shell variable notation

Misspelling the key name

Redis TYPE command expects the key name without quotes or variable symbols.

4fill in blank

hard

Fill both blanks to check the type of key 'cache:data'.

Redis

TYPE [1][2]

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

Acache

Bcache:data

C:data

Dcache_data

Attempts:

3 left

💡 Hint

Common Mistakes

Splitting the key name into two separate arguments

Replacing ':' with '_'

Using only part of the key name

The key name 'cache:data' must be provided as a single argument without splitting it into parts.

5fill in blank

hard

Fill all three blanks to check the type of key 'user:profile:100'.

Redis

TYPE [1][2][3]

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

Auser

B:profile

C:100

Duser_profile_100

Attempts:

3 left

💡 Hint

Common Mistakes

Replacing colons with underscores

Omitting parts of the key name

Adding spaces between parts

The key 'user:profile:100' includes two colons ':' separating parts. You must provide the full key name exactly as it is.

Practice

1. What does the Redis TYPE command do?

easy

A. It deletes the key from the database.

B. It sets a new value for the key.

C. It returns the data type stored at a given key.

D. It lists all keys in the database.

Solution

1. Step 1: Understand the purpose of TYPE command

   The TYPE command is used to find out what kind of data is stored at a specific key in Redis.

2. Step 2: Compare with other commands

   Unlike commands that delete, set, or list keys, TYPE only returns the data type like string, list, or none.

3. Final Answer:

   It returns the data type stored at a given key. -> Option C

4. Quick Check:

   TYPE command = returns key data type [OK]

Hint: TYPE shows key's data type before operations [OK]

Common Mistakes:

• Confusing TYPE with DEL command
• Thinking TYPE changes data
• Assuming TYPE lists keys

2. Which of the following is the correct syntax to check the type of a key named user:1 in Redis?

easy

A. TYPE user:1

B. GET TYPE user:1

C. CHECKTYPE user:1

D. TYPE(key=user:1)

Solution

1. Step 1: Recall Redis TYPE command syntax

   The correct syntax is simply TYPE keyname, so for key user:1, it is TYPE user:1.

2. Step 2: Identify incorrect syntax options

   Options B, C, and D use invalid commands or formats not supported by Redis.

3. Final Answer:

   TYPE user:1 -> Option A

4. Quick Check:

   Correct syntax = TYPE keyname [OK]

Hint: Use TYPE followed by key name directly [OK]

Common Mistakes:

• Adding extra keywords like GET or CHECKTYPE
• Using parentheses or wrong command names
• Confusing with other Redis commands

3. Given these Redis commands executed in order:

SET name "Alice"
LPUSH colors "red"
SADD tags "new"
TYPE name
TYPE colors
TYPE tags
TYPE age

What will be the output of the last four TYPE commands respectively?

medium

A. ["none", "list", "set", "string"]

B. ["string", "set", "list", "none"]

C. ["list", "string", "set", "none"]

D. ["string", "list", "set", "none"]

Solution

1. Step 1: Identify data types set by commands

   SET name "Alice" creates a string key.
   LPUSH colors "red" creates a list.
   SADD tags "new" creates a set.
   age key is not set, so it does not exist.

2. Step 2: Match TYPE outputs to keys

   TYPE name returns "string".
   TYPE colors returns "list".
   TYPE tags returns "set".
   TYPE age returns "none" because key does not exist.

3. Final Answer:

   ["string", "list", "set", "none"] -> Option D

4. Quick Check:

   TYPE outputs = [string, list, set, none] [OK]

Hint: Match commands to Redis data types exactly [OK]

Common Mistakes:

• Mixing up list and set types
• Assuming missing keys return error instead of none
• Confusing string with other types

4. You run the command TYPE mykey but get an unexpected output. Which of these is a likely cause?

medium

A. You used TYPE with wrong syntax like TYPE(mykey).

B. You tried to use TYPE on a key with a value longer than 100 characters.

C. The Redis server is down.

D. The key mykey does not exist in the database.

Solution

1. Step 1: Check command syntax

   Redis TYPE command requires syntax: TYPE keyname without parentheses. Using TYPE(mykey) causes syntax error or unexpected output.

2. Step 2: Evaluate other options

   If key does not exist, TYPE returns "none" (not unexpected). Server down causes connection errors, not TYPE output. Value length does not affect TYPE command.

3. Final Answer:

   You used TYPE with wrong syntax like TYPE(mykey). -> Option A

4. Quick Check:

   Correct syntax needed = TYPE keyname [OK]

Hint: Avoid parentheses in TYPE command syntax [OK]

Common Mistakes:

• Using parentheses with TYPE command
• Confusing missing key output with errors
• Blaming value size for TYPE issues

5. You want to write a Redis script that checks the type of a key and performs different actions based on it. Which sequence correctly uses the TYPE command and handles the case where the key does not exist?

hard

A. Use EXISTS key and if true, assume type is "string".

B. Use TYPE key to get type, then check if result is "none" before proceeding.

C. Use GET key and if it returns null, assume type is "none".

D. Use TYPE key and ignore the "none" result since it means key is empty.

Solution

1. Step 1: Use TYPE command to get key type

   The TYPE command returns the exact data type or "none" if the key does not exist.

2. Step 2: Check for "none" result before actions

   Before performing actions, check if TYPE returned "none" to handle missing keys properly.

3. Final Answer:

   Use TYPE key to get type, then check if result is "none" before proceeding. -> Option B

4. Quick Check:

   Check TYPE result for "none" to handle missing keys [OK]

Hint: Always check TYPE output for "none" before actions [OK]

Common Mistakes:

• Assuming GET null means type is string
• Assuming EXISTS means type is string
• Ignoring "none" type results