Hash类型

Hash 类型，也叫散列，其value是一个无序字典，类似于HashMap结构。

String结构是将对象序列化为JSON字符串存储，当需要修改对象某个字段时很不方便：

KEY	VALUE
demo:user:1	{"id": 1, "name": "JEEK", "age": 18}
demo:product:1	{"id": 1, "name": "redis", "price": 199}

Hash结构可以讲对象中的每个字段独立存储，可以针对单个字段做CRUD:

KEY	FIELD	VALUE
demo:user:1	id	1
	name	JEEK
	age	18
demo:product:1	id	1
	name	redis
	price	199

Hash常见命令有：

• HSET key field value: 添加或者修改hash类型key的field的值
• HGET key field: 获取一个hash类型key的field的值
• HMSET: 批量添加多个hash类型key的field的值
• HMGET: 批量获取多个hash类型的key中的所有的field和value
• HKEYS: 获取一个hash类型的key中的所有的field
• HVALS: 获取一个hash类型key的所有的value
• HINCRBY: 让一个hash类型的key的字段值自增并制定步长
• HSETNX: 添加一个hash类型的key的field值，前提是这个field不存在，否则不执行

127.0.0.1:6379> HMSET user:jeek name jeek age 18
"ok"
127.0.0.1:6379> hget user:jeek name
"jeek"

127.0.0.1:6379> HGETALL user:jeek
1) "name"
2) "jeek"
3) "age"
4) "18"


127.0.0.1:6379> help @HASH

  HDEL key field [field ...]
  summary: Delete one or more hash fields
  since: 2.0.0

  HEXISTS key field
  summary: Determine if a hash field exists
  since: 2.0.0

  HGET key field
  summary: Get the value of a hash field
  since: 2.0.0

  HGETALL key
  summary: Get all the fields and values in a hash
  since: 2.0.0

  HINCRBY key field increment
  summary: Increment the integer value of a hash field by the given number
  since: 2.0.0

  HINCRBYFLOAT key field increment
  summary: Increment the float value of a hash field by the given amount
  since: 2.6.0

  HKEYS key
  summary: Get all the fields in a hash
  since: 2.0.0

  HLEN key
  summary: Get the number of fields in a hash
  since: 2.0.0

  HMGET key field [field ...]
  summary: Get the values of all the given hash fields
  since: 2.0.0

  HMSET key field value [field value ...]
  summary: Set multiple hash fields to multiple values
  since: 2.0.0

  HSCAN key cursor [MATCH pattern] [COUNT count]
  summary: Incrementally iterate hash fields and associated values
  since: 2.8.0

  HSET key field value
  summary: Set the string value of a hash field
  since: 2.0.0

  HSETNX key field value
  summary: Set the value of a hash field, only if the field does not exist
  since: 2.0.0

  HSTRLEN key field
  summary: Get the length of the value of a hash field
  since: 3.2.0

  HVALS key
  summary: Get all the values in a hash
  since: 2.0.0