DECR command in redis

DECR key

Decrement the number stored at key by one. If the key does not exist or contains a value of the wrong type, set the key to the value of "0" before performing the decrement operation.

TIME COMPLEXITY: O(1).

Note: DECR commands are limited to 64-bit signed integers.

RETURN VALUE: Integer reply, this command will reply with the new value of the key after the decrement.

Syntax: DECR KEY_NAME

SET redisKey 100

Example 1: When the value of the key is an integer and in the range of 64-bit.

redis:6379> SET redisKey 100
"OK"
redis:6379> 

redis:6379> DECR redisKey
(integer) 99

Output:

99

Example 2: When the value of the key is not an integer.

redis:6379> SET redisKey1 100.99
"OK"
redis:6379> DECR redisKey1
(error) value is not an integer or out of range

Output:

(error) value is not an integer or out of range

Example 3: When the value of the key is out of range of 64-bit.

redis:6379> SET redisKey2 1.8446744e+20
"OK"
redis:6379> 
redis:6379> DECR redisKey2
(error) value is not an integer or out of range

Output:

(error) value is not an integer or out of range