1. Brief description

The key value types supported by Redis are String character type, map hash type, list list list type, set collection type, sortedset ordered collection type.This article summarizes the use of these key value types and introduces the Keys command. Although the syntax is simple, it needs more practice because of the large number.

2. String Character Types

1. Assignment

Syntax: SET key value

127.0.0.1:6379> set test 123
OK

2. Value

Syntax: GET key

127.0.0.1:6379> get test
"123"

3. Value and assign

Syntax: GETSET key value

127.0.0.1:6379> getset s2 222
"111"
127.0.0.1:6379> get s2
"222"

4. Set/Get Multiple Key Values

Grammar:

• MSET key value [key value ...]
• MGET key [key ...]

127.0.0.1:6379> mset k1 v1 k2 v2 k3 v3
OK
127.0.0.1:6379> get k1
"v1"
127.0.0.1:6379> mget k1 k3
1) "v1"
2) "v3"

5. Delete

Syntax: DEL key

127.0.0.1:6379> del test
(integer) 1

6. Value increase or decrease

a. Incremental numbers

When the stored string is an integer, redis provides a useful command, INCR, that increments the current key value and returns the incremented value.

Syntax: INCR key

127.0.0.1:6379> incr num
(integer) 1
127.0.0.1:6379> incr num
(integer) 2
127.0.0.1:6379> incr num
(integer) 3

b. Increase specified integer

Syntax: INCRBY key increment

127.0.0.1:6379> incrby num 2
(integer) 5
127.0.0.1:6379> incrby num 2
(integer) 7
127.0.0.1:6379> incrby num 2
(integer) 9

c. Decreasing values

Syntax: DECR key

127.0.0.1:6379> decr num
(integer) 9
127.0.0.1:6379> decr num
(integer) 8

d. Reduce specified integer

Syntax: DECRBY key decrement

127.0.0.1:6379> decr num
(integer) 6
127.0.0.1:6379> decr num
(integer) 5
127.0.0.1:6379> decrby num 3
(integer) 2
127.0.0.1:6379> decrby num 3
(integer) -1

7. Append value to tail

append appends the value to the end of the key value.If the key does not exist, set the value of the key to value, which is equivalent to set key value.The return value is the total length of the appended string.

Syntax: APPEND key value

127.0.0.1:6379> set str hello
OK
127.0.0.1:6379> append str " world!"
(integer) 12
127.0.0.1:6379> get str
"hello world!"

8. Get String Length

The STRLEN command returns the length of the key value, or 0 if the key does not exist.

Syntax: STRLEN key

127.0.0.1:6379> strlen str
(integer) 0
127.0.0.1:6379> set str hello
OK
127.0.0.1:6379> strlen str
(integer) 5

3. map hash type

In redis, map is also called hash.Assuming a User object is stored in Redis as JSON serialization, and a User object has attributes such as id, username, password, age, name, etc., the stored procedure is as follows:

What should I do if the business only updates the age attribute, and the other attributes do not update?If the above method still causes waste of resources in transmission and processing, hash can solve this problem very well.

Introduction to redis hash

Hash is called hash type and provides mapping of fields and field values.Field values can only be of string type.
Other types such as hash type, collection type, etc. are not supported.The following:

1. Assignment

The HSET command does not distinguish between an insert and a temporary update operation, and returns 1 when an insert operation is performed and 0 when an update operation is performed.

Set one field value at a time

Syntax: HSET key field value

127.0.0.1:6379> hset user username zhangesan
(integer) 1

Setting multiple field values at once

Syntax: HMSET key field value [field value...]

127.0.0.1:6379> hmset user age 20 username lisi
OK

Assignment when the field does not exist, similar to HSET, except that if the field exists, the command does nothing

Syntax: HSETNX key field value

127.0.0.1:6379> hsetnx user age 30 
(integer) 0

2. Value

Get one field value at a time

Syntax: HGET key field

127.0.0.1:6379> hget user username
"zhangesan"

Get multiple field values at once

Syntax: HMGET key filed[field...]

127.0.0.1:6379> hmget user age username
1) "20"
2) "lisi"

Get all field values

Syntax: HGETALL key

127.0.0.1:6379> hgetall user
1) "age"
2) "20"
3) "username"
4) "lisi"

3. Delete Field

One or more fields can be deleted, and the return value is the number of fields deleted.

Syntax: HDEL key field [field...]

127.0.0.1:6379> hdel user age
(integer) 1
127.0.0.1:6379> hdel user age name
(integer) 0
127.0.0.1:6379> hdel user age username
(integer) 1

4. Increase Numbers

Syntax: HINCRBY key field increment

127.0.0.1:6379> hincrby user age 2  Increase user's age by 2
(integer) 22
127.0.0.1:6379> hget user age       Get the age of the user
"22"

5. Determine whether a field exists

Syntax: HEXISTS key field

127.0.0.1:6379> hexists user age    See user Is there any age field
(integer) 1
127.0.0.1:6379> hexists user name   See user Is there any name field
(integer) 0

6. Get only the field name or value

Grammar:

• HKEYS key
• HVALS key

    127.0.0.1:6379> hmset user age 20 name lisi
    OK
    127.0.0.1:6379> hkeys user
    1) "age"
    2) "name"
    127.0.0.1:6379> hvals user
    1) "20"
    2) "lisi"

7. Get Number of Fields

Syntax: HLEN key

127.0.0.1:6379> hlen user
(integer) 2

4. list List Type

The difference between Arraylist and linkedlist

• ArrayList uses arrays to store data with the following features: fast queries, slow growth and deletion
• LinkedList uses a two-way chain table to store data. It is characterized by fast growth and deletion, slow query, but fast query of data at both ends of the chain table.

The list of redis is stored in a chain table, so the operation of the list data type of redis is to operate on both ends of the list.

1. Add elements to both ends of the list

Add elements to the left of the list

Syntax: LPUSH key value [value...]

127.0.0.1:6379> lpush list1 1 2 3
(integer) 3

Add elements to the right of the list

127.0.0.1:6379> rpush list1 4 5 6
(integer) 3

2. View List

The LRANGE command is one of the most common commands for list types. Getting a fragment in a list returns all elements (including elements at both ends) between start and stop, with an index starting at 0.Indexes can be negative numbers, such as:'-1'represents the rightmost element.

Syntax: LRANGE key start stop

127.0.0.1:6379> lrange list1 0 2
1) "1"
2) "2"
3) "3"
127.0.0.1:6379> lrange list1 0 -1
1) "1"
2) "2"
3) "3"
4) "4"
5) "5"
6) "6"

3. Pop elements from both ends of the list

The LPOP command pops up an element from the left of the list in two steps:
Step 1: Remove the elements to the left of the load list from the list
Step 2: Return the removed element value.

Grammar:

• LPOP key
• RPOP key

    127.0.0.1:6379> lpop list1
    "1"
    127.0.0.1:6379> rpop list1
    "6"

4. Get the number of elements in the list

Syntax: LLEN key

127.0.0.1:6379> llen list1
(integer)4

5. Delete the value specified in the list

The LREM command deletes the elements in the list whose first count value is value, returning the actual number of elements deleted.This command will execute differently depending on the count value.

• When count > 0, LREM is deleted from the left of the list.
• When count <0, LREM is deleted from the right side of the list.
• When count=0, LREM deletes all elements with value.

Syntax: LREM key count value

127.0.0.1:6379> lrem list1 1 4  Remove elements with a value of 4 from the left
(integer)1

6. Get/set the element value of the specified index

Gets the element value of the specified index

Syntax: LINDEX key index

127.0.0.1:6379> lindex list1 2
"5"

Set element value for specified index

Syntax: LSET key index value

127.0.0.1:6379> lset list1 2 4
OK
127.0.0.1:6379> lrange list1 0 -1
1) "2"
2) "3"
3) "4"

7. Keep only the fragments specified in the list

Specified scope is consistent with LRANGE

Syntax: LTRIM key start stop

127.0.0.1:6379> lrange list1 0 -1
1) "2"
2) "3"
3) "4"
127.0.0.1:6379> ltrim list1 0 1
OK
127.0.0.1:6379> lrange list1 0 -1
1) "4"

8. Insert an element into the list

This command first looks for pivot-valued elements from left to right in the list, then decides whether to insert a value before or after the element based on whether the second parameter is BEFORE or AFTER.

Syntax: LINSERT key BEFORE|AFTER pivot value

127.0.0.1:6379> lrange list1 0 -1
1) "4"
127.0.0.1:6379> linsert list1 after 4 5
(integer) 2
127.0.0.1:6379> lrange list1 0 -1
1) "4"
2) "5"

9. Transfer elements from one list to another

Syntax: RPOPLPUSH source destination

127.0.0.1:6379> rpoplpush list1 list2
"5"
127.0.0.1:6379> lrange list2 0 -1
1)"5"
127.0.0.1:6379> lrange list1 0 -1
1) "4"

5. set Collection Type

The difference between set and list:

• Set type: Unordered, non-repeatable
• List type: ordered, repeatable

1. Add/Remove Elements

Syntax: SADD key member [member...]

127.0.0.1:6379> sadd set1 a b c
(integer)3
127.0.0.1:6379> sadd set1 a
(integer)0

Syntax: SREM key memeber [member...]

127.0.0.1:6379> srem set1 c d   d Not in collection, so only remove c
(integer)1

2. Get all the elements in the collection

Syntax: SMEMBERS key

127.0.0.1:6379> smemebers set1
1)"b"
1)"a"

3. Determine if an element is in a set

Syntax: SISMEMBER key member

127.0.0.1:6379> sismember set1 a
(integer)1
127.0.0.1:6379> sismember set1 h
(integer)0

4. Operational commands

a. Difference set operation of sets A - B

A collection of elements belonging to A and not B.

Syntax: SDIFF key [key...]

127.0.0.1:6379> sadd setA 1 2 3
(integer)3
127.0.0.1:6379> sadd setB 2 3 4
(integer)3
127.0.0.1:6379> sdiff setA setB
1)"1"
127.0.0.1:6379> sdiff setB setA
1)"4"

B. Intersection operation of sets A_B

A collection of elements belonging to A and B.

Syntax: SINTER key [key...]

127.0.0.1:6379> sinter setA setB
1)"2"
2)"3"

c. Union operation of sets A_B

A collection of elements belonging to A or B.

Syntax: SUNION key [key...]

127.0.0.1:6379> sunion setA setB
1) "1"
2) "2"
3) "3"
4) "4"

5. Get the number of elements in the collection

Syntax: SCARD key

127.0.0.1:6379> smembers setA
1) "1"
2) "2"
3) "3"
127.0.0.1:6379> scard setA
(integer)3

6. Pop an element out of a collection

Note: Since the set is out of order, the SPOP command randomly selects an element from the set to pop up.

Syntax: SPOP key

127.0.0.1:6379> spop setA
"1"

6. sortedset ordered set type

Sortedset, also known as zset, is an ordered set that can be sorted but unique.Sortedset differs from set in that it adds a score to the elements in the set and sorts them by that score.

1. Add Elements

Add an element and its fraction to an ordered set, and if the element already exists, replace the original fraction with a new fraction.The return value is the number of elements that are newly added to the collection and does not contain elements that previously existed.

Syntax: ZADD key score member [score member...]

127.0.0.1:6379> zadd scoreboard 80 zhangesan 89 lisi 94 wangwu
(integer)3
127.0.0.1:6379> zadd scoreboard 97 lisi
(integer)0

2. Get the fraction of an element

Syntax: ZSCORE key member

127.0.0.1:6379> zscore scoreboard lisi
"97"

3. Delete Elements

Remove one or more members from the ordered set key, and nonexistent members will be ignored.
An error is returned when the key exists but is not an ordered set type.

Syntax: ZREM key member [member...]

127.0.0.1:6379> zrem scoreboard lisi
(integer)1

4. Get a list of elements ranked in a range

a. Returns all elements (including elements at both ends) indexed from start to stop in the order from smallest to largest element fractions

Syntax: ZRANGE key start stop [WITHSCORES]

127.0.0.1:6379> zrange scoreboard 0 2
1)"zhangesan"
2)"wangwu"
3)"lisi"

b. Returns all elements (including elements at both ends) indexed from start to stop in the order of element fraction from large to small

Syntax: ZREVRANGE key start stop [WITHSCORES]

127.0.0.1:6379> zrevrange scoredboard 0 2
1)"lisi"
2)"wangwu"
3)"zhangesan"

If you need to get a fraction of an element, you can add the WITHSCORES parameter at the end of the command

127.0.0.1:6379> zrange scoreboard 0 1 WITHSCORES
1) "zhangsan"
2) "80"
3) "wangwu"
4) "94"

5. Get ranking of elements

a. From small to large

Syntax: ZRANK key member

127.0.0.1:6379> zrank scoreboard lisi
(integer)0

b. From large to small

Syntax: ZREVRANK key member

127.0.0.1:6379> zrevrank scoreboard zhangsan
(integer)1

6. Get the elements of the specified score range

Syntax: ZRANGEBYSCORE key min max [WITHSCORES][LIMIT offset count]

127.0.0.1:6379> zrangebyscore scoreboard 90 97 WITHSCORES
1) "wangwu"
2) "94"
3) "lisi"
4) "97"
127.0.0.1:6379> zrangebyscore scoreboard 70 100 limit 1 2
1) "wangwu"
2) "lisi"

7. Increase the fraction of an element

The return value is the changed score

Syntax: ZINCRBY key increment member

127.0.0.1:6379> zincrby scoreboard 4 lisi
"101"

8. Get the number of elements in the collection

Syntax: ZCARD key

127.0.0.1:6379> zcard scoreboard
(integer)3 

9. Get the number of elements within the specified score range

Syntax: ZCOUNT key min max

127.0.0.1:6379> zcount scoreboard 80 90
(integer) 1

10. Delete elements by rank range

Syntax: ZREMRANGEBYRANK key start stop

127.0.0.1:6379> zremrangebyrank scoreboard 0 1
(integer)2
127.0.0.1:6379> zrange scoreboard 0 -1
1)"lisi"

11. Delete elements by score range

Syntax: ZREMRANGEBYSCORE key min max

127.0.0.1:6379> zadd scoreboard 84 zhangsan
(integer)1
127.0.0.1:6379> zremrangebyscore scoreboard 80 100
(integer)1

7. Keys Command

1,keys

Returns all key s that satisfy a given pattern

127.0.0.1:6379> keys mylist*
1) "mylist"
2) "mylist5"
3) "mylist6"
4) "mylist7"
5) "mylist8"

2,exists

Confirm the existence of a key
Example: From the results, the key Hong Wan does not exist in the database, but the key age does exist

127.0.0.1:6379> exists HongWan
(integer)0
127.0.0.1:6379> exists age
(integer)1

3,del

Delete a key

127.0.0.1:6379> del age
(integer)1
127.0.0.1:6379> exists age
(integer)0

4,rename

Rename key
Example: Change age to age_new.

127.0.0.1:6379> keys *
1) "age"
127.0.0.1:6379> rename age age_new
OK
127.0.0.1:6379>keys *
1) "age_new"

5,type

Type of return value
Example: Determine the type of value

127.0.0.1:6379> type addr
string
127.0.0.1:6379> type myzset2
set
127.0.0.1:6379> type mylist
list

6. Set the key's lifetime

redis are more often used as caches in practice, but cached data generally requires a lifetime, that is, data is destroyed after expiration.

EXPIRE key seconds sets the key's lifetime in seconds. The key is automatically deleted after how many seconds
 TTL key sets the remaining lifetime of the key
 PERSIST key Clear Lifetime
 PEXPIRE key milliseconds lifetime is set in milliseconds

Example:

127.0.0.1:6379> set test 1      Set up test Value of 1
OK
127.0.0.1:6379> get test        Obtain test Value of
"1"
127.0.0.1:6379> EXPIRE test 5   Set up test Lifetime is 5 seconds
(integer)1
127.0.0.1:6379> TTL test        See test Generation time of 1 second to delete
(integer)1
127.0.0.1:6379> TTL test
(integer) -2
127.0.0.1:6379> get test        Obtain test Value of, deleted
(nil)