The following commands can be used to update a field in a Redis hash. The command we use will depend on the type of data that’s stored in the field.

The HSET Command

The HSET command can be used to update the value at the given field.

Suppose we set a hash like this:

 HSET pet name "Wag" age 10 height 7.85

Result:

(integer) 3

Let’s use HGET to check the value of the name field:

HGET pet name

Result:

"Wag"

We can use the HSET command to update that field’s value:

 HSET pet name "Bark"

Result:

(integer) 0

An integer reply of zero means that no new fields were added. However, our existing field was updated.

Let’s check:

HGET pet name

Result:

"Bark"

It has been updated as specified.

The HINCRBY Command

The HINCRBY command increments the number stored at a field by the specified amount. This command is limited to 64 bit signed integers, therefore, we would only use it on fields that contain integers:

HINCRBY pet age 1

Result:

(integer) 11

The integer reply tells us the value of the field after it has been incremented. The original value of this field was 10, and we incremented it by 1. Therefore, the new value is 11 as indicated in the result.

Let’s check the value of that field now:

HGET pet age

Result:

"11"

As expected.

The HINCRBYFLOAT Command

The HINCRBYFLOAT command is similar to HINCRBY but it is intended to be used on floating point numbers. Let’s update the height field:

HINCRBYFLOAT pet height 1.27

Result:

"9.12"

The bulk string reply tells us the value of the field after it has been incremented.

Let’s use the HGETALL command to check the contents of the hash now:

HGETALL pet

Result:

1) "name"
2) "Bark"
3) "age"
4) "11"
5) "height"
6) "9.12"