Redis Data Types

Redis supports five data types: string (string), hash (hash), list (list), set (set), and zset (sorted set: ordered set).

String (String)

The string is the most basic type in Redis, which you can understand as exactly the same as Memcached, with one key corresponding to one value.

The string type is binary safe. It means that Redis's string can contain any data. For example, jpg images or serialized objects.

The string type is the most basic data type of Redis, and the maximum storage capacity of the string type value can be 512MB.

Online Examples

redis　127.0.0.1:6379>　SET　w3codebox "Basic Tutorial Website"
OK
redis　127.0.0.1:6379>　GET　w3codebox
"Basic Tutorial Website"

In the above example, we used Redis's SET and GET command. The key is w3codebox, the corresponding value is Basic Tutorial Website.

Note:The maximum storage capacity of a key is 512MB.

Hash (hash)

Redis hash is a collection of key-value (key=>value) pairs.

Redis hash is a mapping table of string type field and value, which is particularly suitable for storing objects.

Online Examples

DEL w3codebox is used to delete the key used in the previous test, otherwise an error will occur:(error) WRONGTYPE Operation against a key holding the wrong kind of value

redis　127.0.0.1:6379> DEL w3codebox
redis　127.0.0.1:6379>　HMSET　w3codebox field1　"Hello" field2　"World"
"OK"
redis　127.0.0.1:6379>　HGET　w3codebox field1
"Hello"
redis　127.0.0.1:6379>　HGET　w3codebox field2
"World"

In the example, we used Redis HMSET, HGET command,HMSET Two field=>value pairs are set, HGET gets the corresponding field corresponding to value.

Each hash can store 2³² -1 Key-value pair (4More than zero billion).

List (list)

Redis list is a simple string list, sorted in the order of insertion. You can add an element to the beginning (left) or the end (right) of the list.

Online Examples

redis　127.0.0.1:6379> DEL w3codebox
redis　127.0.0.1:6379>　lpush　w3codebox redis
(integer)　1
redis　127.0.0.1:6379>　lpush　w3codebox mongodb
(integer)　2
redis　127.0.0.1:6379>　lpush　w3codebox rabbitmq
(integer)　3
redis　127.0.0.1:6379>　lrange　w3codebox 0　10
1) "rabbitmq"
2) "mongodb"
3) "redis"
redis　127.0.0.1:6379>

The list can store at most 　2³² - 1 elements (4294967295, each list can store4More than zero billion).

Set (collection)

Redis's Set is an unordered collection of string types.

The set is implemented by a hash table, so the complexity of adding, deleting, and searching is O(1)。

sadd command

Add a string element to the set collection corresponding to the key, return on success 1If the element is already in the set, return 0.

sadd key member

Online Examples

redis　127.0.0.1:6379> DEL w3codebox
redis　127.0.0.1:6379> SADD w3codebox redis
(integer)　1
redis　127.0.0.1:6379> SADD w3codebox mongodb
(integer)　1
redis　127.0.0.1:6379> SADD w3codebox rabbitmq
(integer)　1
redis　127.0.0.1:6379> SADD w3codebox rabbitmq
(integer) 0
redis　127.0.0.1:6379> SMEMBERS w3codebox
1) "redis"
2) "rabbitmq"
3) "mongodb"

Note:In the above example, rabbitmq was added twice, but according to the uniqueness of the elements in the set, the second inserted element will be ignored.

The maximum number of members in the set is 　2³² 　- 1(4294967295, each set can store4(0 to 1 billion members).

zset(sorted set: ordered set)

Like set, zset in Redis is also a collection of string type elements and does not allow duplicate members.

The difference is that each element is associated with a double-type score. Redis sorts the members of the set from small to large through scores.

The members of zset are unique, but the scores (score) can be repeated.

ZADD Command

Add an element to the set, if the element already exists in the set, update the corresponding score

ZADD key score member

Online Examples

redis　127.0.0.1:6379> DEL w3codebox
redis　127.0.0.1:6379> ZADD w3codebox 0 redis
(integer)　1
redis　127.0.0.1:6379> ZADD w3codebox 0 mongodb
(integer)　1
redis　127.0.0.1:6379> ZADD w3codebox 0 rabbitmq
(integer)　1
redis　127.0.0.1:6379> ZADD w3codebox 0 rabbitmq
(integer) 0
redis　127.0.0.1:6379> ZRANGEBYSCORE w3codebox 0　1000
1) "mongodb"
2) "rabbitmq"
3) "redis"