Redis Datatypes and Commands-String

Redis Datatypes and Commands – String

Redis stores the data as key value pair. Keys can be any binary value and it is represented as ASCII strings for easily understandable and readability purpose. Redis supports five different datatypes and anyone of the datatype can be represented as value.

datatypes

Redis supports five different datatypes and they are given below. Each datatype can be used in Redis with different set of commands.

  • String
  • List
  • Set
  • Sorted Set
  • Hash

string

String is a datatype used in Redis to store the Key value pair. The value can be represented as String. String is a sequence of characters and binary safe in Redis.

set and get

The Set command is used to create a new key value pair data in Redis. Execute the below command on the Redis client to create a new value pair data.

Syntax
set <keyname> <value>

Example
set employee John

The Get command is used to fetch the value by using key name. Execute the below command on the Redis client to fetch the value by using key name.

Syntax
get <keyname>

Example
get employee

If you want to set the new value for existing key, then you can use the same Set command. The Set command doesn’t append the new value with existing one. It overrides the existing value with new one.

Example
set employee Mike
set and get commands

If you want to set the values for the key like employee First Name and Last Name, then use the below command on the Redis client. The value must be provided within double quotes.

Syntax
set <keyname> "<value>"

Example
set employee "John Mike"
The value provided within double quotes

naming a key

If you want to store the more than one employee details with unique ID, then use the key name like below.

Syntax
set <keyname>:<uniqueID> value

Example
set employee:1 John
set employee:2 Mike
set employee:3 Lawrence
Redis keys with unique Id

Execute the below command on the Redis client to fetch all available keys.

keys *
to view all keys

Setting up new key value pair data once again to see the new key on the list of available keys.

set student "James"
get student
setting up new key value pair

Now, execute the below command once again to view the list of available keys.

keys *
To view list of available keys

Use the below command, to fetch the list of available keys starts with sequence of characters.

Syntax
keys <pattern>

Example
keys emp*
keys starts with

time to live

Use the below command to set the expire time for the key. The expire time must be provided by using seconds or milliseconds.

Syntax
set <keyname> <value> ex <no:of:seconds>

Example
set employee:4 Kite ex 30

Use the below command to view the remaining time of the key after set the expire time. The command name is “Time To Live”. The negative value on the TTL represented key has expired. The NIL value will return, while fetching the value by using key after expired.

Syntax
ttl <keyname>

Example
ttl employee:4
TTL command

key not exists – nx

Use the below command to set key value pair data, if the key is not exists on the Redis database.

Syntax
set <keyname> <value> NX

Example
set employee:4 Fidel NX
Key Not exists

key exists – xx

Use the below command to set the key value pair data, if the key is already exists on the Redis database. If the Key is already not exists, then the Redis client will return “NIL”.

Syntax
set <keyname> <value> XX

Example
set employee:4 Nathan XX
set employee:5 Nathan XX
Key already exists

exists

Use the below command to check the key is already exists or not on the Redis database.

Syntax
exists <keyname>

Example
exists employee:4
exists employee:5

append

Execute the below command to append the value for existing key value pair data.

Syntax
append <keyname> <newvalue>

Example
set employee:5 Vikram
get employee:5
append employee:5 " Karthik"
get employee:5
Append command

string length

To find the length of the value by using key, execute the below command. The return value will be Integer.

Syntax
strlen <keyname>

Example
strlen employee:5
String length

incr and decr

Use the below command to Increment and Decrements the Integer value by using key. By default Increment increase the value by 1 and Decrements decreases the value by 1.

Syntax - Increment
incr <keyname>
incrby <keyname> <incrementvalue>

Syntax - Decrement
decr <keyname>
decrby <keyname> <decrementvalue>

Example
set testkey 1 
incr testkey  
incrby testkey 20 
decr testkey 
decrby testkey 10 
get testkey 
Increment and Decrements

mset and mget

Use the below commands, to set and get the multiple key value pair by using single command.

Syntax
mset <keyname1> <value1> <keyname2> <value2>
mget <keyname1> 
mget <keyname1> <keyname2>

Example
mset firstkey firstvalue secondkey secondvalue
mget firstkey
mget firstkey secondkey
mset and mget commands

We have learned the basic Redis String commands.

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