Redis数据类型--string
Redis数据类型--string 五种数据类型：string, list, set, zset, hash 1). string类型 String是最简单的类型，一个key对应一个value，string类型是二进制安全的。Redis的string可以包含任何数据，比如jpg图片或者序列化的对象(PHP中对象序列化函数serialize)
Redis数据类型--string
五种数据类型：string, list, set, zset, hash
1). string类型
String是最简单的类型，一个key对应一个value，string类型是二进制安全的。Redis的string可以包含任何数据，比如jpg图片或者序列化的对象(PHP中对象序列化函数serialize)
内部实现，其本质是一个byte数组，字符串的大小被限制在512M以内
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[plain]
struct sdshdr {
long len; //buf数组的长度
long free; //buf数组中剩余可用字节数
char buf[]; //存储实际字符串内容
}
操作方法：
a.set方法：
格式：set key value
设置key对应的值为string类型的value，OK=成功，0=失败, 若是该key已经存在，则覆盖其原有值。
[plain]
>set pwd 123456 //即添加一个pwd=123456的k-v
OK
b.get方法：
格式：get key
获取key对应的string值，如果key不存在返回nil
[plain]
>get pwd //即获取pwd对应的值
"123456"
>get name
(nil)
c.setnx方法：
格式：setnx key value
与set相同，不同的是：设置之前要检测key是否已经存在，如果key已经存在，则返回0，（nx = notexist）
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[plain]
>setnx user zhangsan
(integer) 1
>setnx user lisi
(integer) 0
>get user
"zhangsan"
>set user chuangrain
OK
>get user
"chuangrain"
d. setex方法：
格式：setex key seconds value
设置key对应的值为string类型的value，并指定对此键值对应的有效期seconds
[plain]
>setex tea 10 food //即设置tea=food，指定10秒钟有效时间
OK
>get tea
"food"
>get tea //10s后
(nil)
e.setrange方法：
格式：setrange key offset value
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用value参数调换指定key对应的字符串值 ，从偏移量offset开始，不存在的key当作空白字符串处理，如果offset大于key对应的字符串长度，那么原字符串和偏移量之间的空白将用零比特(zerobytes, "\x00")来填充，返回被setrange修改后的字符串长度。
[plain]
>set hw "hello word"
OK
>setrange hw 6 "Redis"
(integer)11
>get hw
"helloRedis"
>setrange hello 2 "chuang" //hello不存在
(integer) 12
>get hello
"\x00\x00chuangrain"
>setrange hello 15 rd
(integer) 17
>get hello
"\x00\x00chuangrain\x00\x00\x00rd"
f.mset方法
格式：mset key1 value1 key2 value2 …
一次设置多个key的值，成功返回OK，即全部设置成功，失败返回0，即没有任何设置，此操作具有原子性
g.msetnx方法：
格式：msetnx key1 value1 key2 value2 …
与mset类似，不同的是要检查设置的key是否已经存在，若存在返回0
h.getset方法：
格式：getset key value
设置key对应string类型的value，并返回key的旧值，如果key不存在，先设置key=value，再返回nil
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[plain]
>get site
"taobao"
>getset site baidu
"taobao"
>get site
"baidu"
i.getrange方法：
格式：getrange key start end
获取key对应value的子字符串，从start开始到end结束，如果end（为正）小于 start（为正），或者key不存在，则返回空字符串""，如果end超出value的长度，则返 回start到value末尾之间的字符串，start和end可以为负，字符串左边的下标从0开始，右边的下标从-1开始。
0
1
2
3
4
b
a
i
d
u
-5
-4
-3
-2
-1
以"baidu"为例，即每个字符可能通过正、负来访问
[plain]
>get site
"baidu"
>getrange site 1 2
"ai"
>getrange site 3 -1
"du"
>getrange www 3 4 //www不存在
""
j.mget方法
格式：mget key1 key2 …
一次获取多个key对应的value值，如果对应的key不存在，则对应返回nil
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[plain]
>mset user1 taobao user2 baidu
OK
>mget user1 user2 user3 //user3不存在
1) "taobao"
2) "baidu"
3) (nil)
k.incr方法：
格式：incr key
将指定key对应的value原子性的递增1，返回递增后的value值。如果key不存在，设其初始值为0，再递增1。如果value的值不是整型，则会返回失败信息。
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[plain]
>mset key1 44 key2 1.1 key3 taobao
OK
>incr key1
(integer) 45
>get key1
"45"
>incr key2
(error)ERR value is not an integer or out of range
>incr key3
(error)ERR value is not an integer or out of range
>incr key4 //key4不存在
(integer) 1
l.incrby方法：
格式：incrby key decrement
与incr类似，将指定key对应的value原子性的递增decrement，返回递增后的value 值，如果key不存在， 设其初始值为0，再递增decrement。
m.decr方法：
格式：decr key
与incr作用相反，对key对应的value递减1操作，如果key不存在，则设置key 为初始值为0，再递减1。
[plain]
>decrdeepin //deepin不存在
(integer) -1
n.decrby方法：
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格式：decrby key decrement
与incrby相反
o.strlen方法：
格式：strlen key
获取key对应的value的字符串长度，如果key不存在返回nil
p.append方法：
格式：append key value
如果key已经存在，将value的数据追加到已存在的value末尾，如果key不存在， 将创建一个新的key/value。返回新value的长度。
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[plain]
>append site taobao
(integer) 11
>get site
"baidutaobao"
>append test taobao //test不存在
(integer) 6
>get test
"taobao"
q.setbit方法：
格式：setbit key offset value
设置在key对应指定offset上bit的值(value)，该值只能为1或者0，返回该offset上原有的bit值。如果key不存在，将创建一个新值，并在指定的offset上设定bit值。如果offset大于value的字符串长度，redis将拉长value值并在指定offset上设置参数中 的bit值，之间添加的bit值为0。注：offset值必须大于0。
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[plain]
>setbit userkey 7 1 //userkey不存在，从0开始到第2位bit值为1，返回原bit值0
(integer)0
>get userkey
"\x01"//即0000 0001转为16进制
r.getbit方法：
格式：getbit key offset
获取key对应offset上的bit值，如果offset大于value的长度，或者key不存在，或者非二进制型字符串，返回0。
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[plain]
>getbit userkey 7
(integer) 1
>getbit userkey //user1key不存在
(integer) 0
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