Redis INCR Command

The Redis INCR command is used to increment the value of a key by a factor of one. The value associated with the key must be an integer for this command to work. If the specified key does not exist, its value is set to 0 before the command executes.

Although the operation applies to integer values, Redis does not have a specific integer data type. Hence the value to be incremented is a string type that can be represented as a base-10 64 bit signed integer value.

Let us discuss how we can use this command.

Basic Usage

The command’s syntax can be expressed as:

127.0.0.1:6379> INCR key

The command accepts the key as the argument and returns the new value after the increment operation.

For example, start by creating a key as shown:

 127.0.0.1:6379> SET age 23
OK

Next, run the INCR command on the “age” key.

127.0.0.1:6379> INCR age
(integer) 24

The command returns the value of age after incrementing by one.

It is good to keep in mind that the command modifies the value of the key in place. Hence, the value of the key is the one after the increment operation.

For example:

 127.0.0.1:6379> GET age
"24"

DECR Command

If you have a command to increment a value by one, there must be a command to decrement by one, right? Yes. You are right.

Redis also provides you with the DECR command to decrement a value by one. It works very similarly to the INCR command because it takes a key holding an integer value and returns the value after decrement.

The syntax can be expressed as:

127.0.0.1:6379> DECR key

Let us look at a simple example:

Start by creating a simple key as:

127.0.0.1:6379> SET number 1000
OK

Next, decrement the value using the DECR command:

127.0.0.1:6379> DECR number
(integer) 999

As we mentioned, the INCR and DECR command work on an integer value. Redis returns an error as shown below if you use the commands on a non-integer value.

127.0.0.1:6379> SET nonInt "Hello"
127.0.0.1:6379> INCR nonInt
(error) ERR value is not an integer or out of range

INCRBY/DECRBY Commands

Suppose you want to increment a value by a specific integer value. For example, if you’re going to increase a value by 5 using the INCR command, you have to re-run the command five times.

To resolve this, you can use the INCRBY and DECRBY commands to increment or decrement a value by a specific factor, respectively.

The syntax is as shown:

127.0.0.1:6379> INCRBY key increment

The commands take the key and an increment value as the arguments.

For example:

127.0.0.1:6379> SET sample 1500
127.0.0.1:6379> INCRBY sample 1000
(integer) 2500

The commands will return the value after increment or decrement operations.

Closing

It is good to keep the increment and decrement commands at hand to work with Redis. Using this tutorial, you learned how the commands work and use them in a Redis database.

from https://ift.tt/3GYypIe