HINCRBY for numeric fields in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the Redis command HINCRBY do?

HINCRBY increments the integer value of a field in a hash by a given number. If the field does not exist, it is set to 0 before the increment.

beginner

What happens if you use HINCRBY on a field that does not exist in the hash?

The field is created with the value 0, then incremented by the specified amount.

beginner

Can HINCRBY be used to decrement a numeric field in a Redis hash?

Yes, by passing a negative number as the increment, HINCRBY can decrement the field's value.

intermediate

What error occurs if you try to use HINCRBY on a field that contains a non-integer value?

Redis returns an error because HINCRBY only works with integer values.

beginner

Example: What is the result of HINCRBY user:1 visits 3 if visits was 5 before?

The new value of visits will be 8 (5 + 3).

What does HINCRBY myhash field 10 do if field does not exist?

A Does nothing

B Returns an error

C Creates <code>field</code> with value 10

D Creates <code>field</code> with value 0

If the field does not exist, Redis sets it to 0 then adds 10, so the final value is 10.

Which data type must the field value be for HINCRBY to work?

A Set

B String

C List

D Integer

HINCRBY works only on integer values stored in hash fields.

What happens if you run HINCRBY myhash field -2?

A Increments <code>field</code> by 2

B Decrements <code>field</code> by 2

C Deletes <code>field</code>

D Returns an error

Passing a negative number decrements the field's value by that amount.

If field contains the string "hello", what happens when you run HINCRBY myhash field 1?

A Redis returns an error

B Field becomes 1

C Field becomes "hello1"

D Field is deleted

Redis returns an error because the field value is not an integer.

What is the return value of HINCRBY after incrementing a field?

A The new value after increment

B The increment amount

C Always 0

D The old value before increment

HINCRBY returns the new value of the field after the increment.

Explain how the Redis command HINCRBY works with numeric fields in a hash.

Think about how you add or subtract numbers in a table of values.

What errors or limitations should you be aware of when using HINCRBY?

Consider what happens if you try to add numbers to words.