HKEYS and HVALS in Redis - Step-by-Step Execution

Concept Flow - HKEYS and HVALS

Start with a Redis hash

↓

Run HKEYS command

→Get all field names

↓

Run HVALS command

→Get all field values

↓

Use results as needed

↓

End

You start with a Redis hash, then use HKEYS to get all field names and HVALS to get all field values separately.

Execution Sample

Redis

HSET user:1 name "Alice" age "30" city "NY"
HKEYS user:1
HVALS user:1

This sets a hash with fields name, age, city, then retrieves all keys and all values.

Execution Table

Step	Command	Action	Result
1	HSET user:1 name "Alice" age "30" city "NY"	Create hash user:1 with fields and values	3
2	HKEYS user:1	Retrieve all field names from user:1	["name", "age", "city"]
3	HVALS user:1	Retrieve all field values from user:1	["Alice", "30", "NY"]
4	End	No more commands	Execution complete

💡 All commands executed; HKEYS and HVALS returned all fields and values respectively.

Variable Tracker

Variable	Start	After HSET	After HKEYS	After HVALS	Final
user:1	empty	{"name":"Alice", "age":"30", "city":"NY"}	["name", "age", "city"]	["Alice", "30", "NY"]	unchanged

Key Moments - 2 Insights

Why do HKEYS and HVALS return separate lists instead of pairs?

HKEYS returns only the field names and HVALS returns only the values. To get pairs, you use HGETALL. See execution_table rows 2 and 3.

Does the order of fields in HKEYS match the order of values in HVALS?

Yes, the order of fields from HKEYS matches the order of values from HVALS, so you can pair them by position. See execution_table rows 2 and 3.

Visual Quiz - 3 Questions

Look at the execution table, what does HKEYS user:1 return at step 2?

A ["user:1"]

B ["Alice", "30", "NY"]

C ["name", "age", "city"]

D An error

💡 Hint

Check the 'Result' column in row 2 of the execution_table.

At which step do we get the list of all values in the hash?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look for the command HVALS in the execution_table.

If the hash user:1 had an extra field 'email', how would HKEYS output change?

A It would include 'email' in the list

B It would exclude 'email'

C It would return values instead of keys

D It would cause an error

💡 Hint

HKEYS returns all field names present in the hash as shown in execution_table row 2.

Concept Snapshot

HKEYS key
  - Returns all field names in the hash stored at key.
HVALS key
  - Returns all field values in the hash stored at key.
Order of keys and values matches.
Use HGETALL for key-value pairs.
Both commands return arrays.

Full Transcript

We start with a Redis hash named user:1 with fields name, age, and city set to Alice, 30, and NY respectively. The HKEYS command retrieves all the field names as a list: name, age, city. The HVALS command retrieves all the field values as a list: Alice, 30, NY. The order of keys and values matches, so you can pair them by position. These commands help you get just the keys or just the values from a hash. To get both keys and values together, you would use HGETALL. This trace shows how the hash changes and what each command returns step by step.