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Redis Compared with other non relational databases, the advantage of database mainly lies in the rich data types , Write it down and learn it together redis The data type of the database

One 、String type

String yes redis Most basic types , Maximum energy storage 512MB The data of ,String Type is binary safe , Any data can be stored 、 Such as digital 、 picture 、 Serialized objects, etc

1、set / get / append / strlen

redis-cli		
exists ljm				# Determine whether the key exists , There is returned 1, Otherwise return to 0
append ljm "hello"		# The key does not exist , therefore append The command returns the current value The length of 
append ljm " world"		# The key already exists , So return after append value The length of 
get ljm					# adopt get Command to get the key , To judge append Result 
set ljm "just do it"	# adopt set Command sets a new value for the key , And cover the original value 
get ljm
strlen ljm				# Get specified key The character length of

2、incr / decr / incrby / decrby

exists ac			# Determine whether the key exists 
del ac				# Delete the original key , return 1 Description delete successfully 
set ac 100			# Set a new value for the key 
incr ac			    # The value of this key is incremented 1
decr ac			    # The value of this key decreases 1
incrby ac 10		# The value of this key is incremented by a fixed value 
decrby ac -20		# The value of this key is reduced by a fixed value 
decrby ac 30
get ac			    # View the value of the key 

set ac "hello"	    # The value of this key is set to string 
get ac			    # Check the value 
incr ac			    # Do the self growth operation （ notes ： String types cannot grow by themselves ）

3、getset

get ac
getset ac 0 # While getting the original value of the counter , And set it to the new value , These two operations are done atomically at the same time 
get ac

4、setex


setex ac seconds 15  # Set the specified Key Expires on 15 second 
ttl key    	 					# adopt ttl Command view specified key The remaining life of （ second ）,-2 Indicates that it has expired ,-1 Never expire 
get ac						
ttl ac
ttl ac

5、setnx

del ac
setnx ac 100 # Create specified key , If the key exists, do not execute , If it doesn't exist, execute 
setnx ac 150
get ac

6、mset / mget / msetnx

mset ll "hellow" jj "world"		# The value of the batch setting key 
mget ll jj		    # Batch get key values 
msetnx mm 100 nn 200	# Batch setting key values , If there are existing keys, do not execute 
msetnx ll 150 mm 250

Two 、List type

The element type of the list is string, Sort by insertion order , Add elements to the head or tail of the list

1、lpush / lpushx / lrange

	lpush  	# This command creates the key and its associated List, Then... In the parameter values Insert into the header from left to right 
	lpushx	# This command only if key In existence , take value The value is inserted into the header 
    lrange	# Returns the elements in the specified interval in the list ,0 Represents the first element ,1 For the second element

2、lpop / llen

   lpop		# Remove and return the first element , Start from scratch 
   llen		# Check the number of elements in the list

3、lrem / lset / lindex / ltrim

   lrem		# From the head (left) To the tail (right) Variable linked list , Delete 2 Values equal to a The elements of , The return value is the actual deleted quantity 
   lset		# Set the index value to xxx Set the element value of to the new value xxx
   lindex	# Get index value as xxx The element value of .
   ltrim	# Keep only index values xxx To xxx The elements of

4、linsert

linsert		# At the bottom of the key xxx Element before | Insert new element after

5、rpush / rpushx / rpop / rpoplpush

    rpush		# Insert values from left to right at the end of the table 
   rpushx		# Executes when the specified key exists , Otherwise, do not execute 
   rpop			# Remove and return the first element of the key , Start at the end 
   rpoplpush	# Will key 1 The tail element xxx eject , At the same time, insert the key 2 The head of ( Atomically complete these two steps )

3、 ... and 、Hash type

hash For storing objects . It can be named like this ： Object category and ID Key name , Use fields to represent the properties of objects , Field values store property values .
If Hash It contains very few fields , Then this type of data will only occupy a small amount of disk space . every last Hash Can be stored 4294967295 Key value pairs .

1、hset / hget / hdel / hexists / hlen / hsetnx

 hset			# to xxx The key setting field is xxx, The value is xxx
   hget			# obtain xxx key , Field is xxx Value 
   hdel			# Delete xxx Keyed xxx Field , Successfully returns 1
   hexists		# Judge xxx In the key xxx Whether the field exists , There is returned 1
   hlen			# obtain xxx Number of fields for the key 
   hsetnx		# to xxx Key to add a new field , Whether to execute is based on whether this field exists , Whether the key exists or not , return 1 Indicates successful execution

2、hincrby

hincrby		# to xxx Keyed xxx Field value plus x

3、hmset / hmget / hgetall / hkeys / hvals

hmset key field value   # Batch is xxx Key to create fields and assign values 
hmget key field		    # Get and specify multiple field values 
hgetall key		        # return xxx All fields of the key and their values , It's listed pair by pair 
hkeys key		        # Just get xxx All field names in the key 
hvals key		        # Just get xxx All field values in the key

Four 、Set type （ unordered set ）

unordered set , Element type is String type , Element is unique , Duplicate members are not allowed . Union can be performed between multiple collection types 、 Intersection and subtraction operations .

1、sadd / smembers / scard / sismember

   sadd		        # Add one or more member elements to the collection , Member elements that already exist in the collection will be ignored . If set  key  non-existent , Then create a collection containing only the added elements as members 
   smembers			# adopt smembers Command to view the inserted results , The order of output is independent of the order of insertion 
   scard			# Get the number of members in the collection 
   sismember		# In the judgment key xxx Whether members exist , return 0 Does not exist ,1 Indicates presence

2、spop / srem / srandmember / smove

   spop				# Randomly remove and return a member of the key 
   srem				# Remove... From the key xxx、xxx、xxx member , And return the number of removed members 
   srandmember		# This command randomly returns a member 
   smove 			# Will key 1 Of xxx Move member to key 2, Successfully returns 1, Failure to return 0

5、 ... and 、Sorted Set type （zset、 Ordered set ）

Ordered set , Element type is String, Element is unique , Can't repeat .
Each element is associated with a double Score of type score( Said the weight ), You can sort by weight , Elemental score Can be the same .

1、zadd / zcard / zcount / zrem / zincrby / zscore / zrank

   zadd			# Add one or more member elements and their fractional values to an ordered set 
   zcard		# Get the number of members in the key 
   zcount		# The fraction satisfies the expression x <= score <= x The number of members of 
   zrem		 	# Delete members xxx、xxx, Returns the number of members actually deleted 
   zincrby	 	# member xxx non-existent ,zincrby The command adds the member and assumes that its initial score is 0
   zscore		# Get members xxx The scores of 
   zrank		# Get members xxx Location index value of

2、zrangebyscore / zremrangebyrank / zremrrangebyscore

   zrangebyscore		# Get the score to satisfy the expression  x <= score <= x  Members of 
   zremrangebyrank		# The delete location index satisfies the expression  x <= rank <= x  Members of .
   zremrrangebyscore	# Delete the fraction satisfaction expression  x <= score <= x  Members of , And returns the actual number of deletions .

3、zrevrange / zrevrangebyscore / zrevrank

   zrevrange			# Get and return the members in this interval in the way of location index from high to low 
   zrevrangebyscore		# Get the score to satisfy the expression x >= score >= x  Members of , And output from top to bottom .
   zrevrank	 			# Get member index

summary

String The conventional  set/get  operation ,value It can be String It can also be numbers . Generally do some complex counting function cache hash

 here value It's storing structured objects , It is more convenient to operate one of the fields . When doing single sign on , This data structure is used to store user information , With cookieId As key, Set up 30 Minutes is the cache expiration time , It can simulate the similar session The effect of 

list
 Use List Data structure of , Can do simple message queuing function . There's another one , You can use lrange command , Based on redis The paging function of , Excellent performance , Good user experience .LIST It can complete the queue very well , The first in, first out principle 

set
 because set It's a collection of distinct values . So we can do the function of global de duplication . Why not JVM Self contained Set Deduplication ？ Because our system is generally a cluster deployment , Use JVM Self contained Set, More trouble , Do you want to do a whole thing for one , Another public service , It's too troublesome 
 in addition , Is to use intersection 、 Combine 、 Subtraction and so on , We can calculate common preferences , All my hobbies , Their own unique preferences and other functions 

sorted set
sortedset One more weight parameter score, The elements in the set can press score Arrange . Can do leaderboard application , take TOP N operation

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