Redis basic data type (string)

- Storage type
- Common operation commands
- - set
  - get
  - mset
  - mget
  - getrange
  - strlen
  - append
  - incr
  - incrby
  - incrbyfloat
  - decr
  - decrby
  - of the

Storage type

int (integer), float (single-precision floating-point number), string (string)

Common operation commands

set

command

SET key value [EX seconds] [PX milliseconds] [NX|XX]

Description
Set the key to the specified "string" value.
If the key has saved a value, then this operation will directly overwrite the original value and ignore the original type.
When the set command is executed successfully, the expiration time set before will be invalid
Options
Starting from version 2.6.12, redis has added a series of options to the SET command:
- EX seconds-Set the expiration time of the key, the unit is hour and second
- PX milliseconds-set the key expiration time, the unit is milliseconds
- NX-The value of the key will only be set if the key does not exist
- XX-The value of the key will only be set if the key exists
Note: Since the SET command plus options can completely replace the functions of SETNX, SETEX, PSETEX, in future versions, redis may be deprecated and eventually abandon these commands.
return value

If the SETcommand was executed normally and then return back OK, or if added NXor XXoptions, but do not set conditions. Then it will return nil.

example

redis> SET mykey "Hello"
OK
redis> GET mykey
"Hello"
redis>

get

command
```
GET key
```
Description

Return keyof value. If the key does not exist, return a special value nil. If it keyis valuenot a string, an error is returned, because GETonly strings of type string are processed values.
return value

The value corresponding to the key, or nil (when the key does not exist)

example

redis> GET nonexisting
(nil)
redis> SET mykey "Hello"
OK
redis> GET mykey
"Hello"
redis>

mset

command
```
MSET key value [key value ...]
```
Description

Correspond to the given keys to their corresponding values. MSETWill replace the existing value with the new value, just like a normal SET command. If you don't want to overwrite the existing values, please refer to the command MSETNX .

MSETIt is atomic, so all given keys are set at once. It is impossible for the client to see that some of the keys have been updated and the others have not changed.
return value

Always OK, because MSET will not fail.

example

redis> MSET key1 "Hello" key2 "World"
OK
redis> GET key1
"Hello"
redis> GET key2
"World"
redis>

mget

command
```
MGET key [key ...]
```
Description

Returns the value of all the specified keys. For each key that does not correspond to a string or does not exist, a special value is returned nil. Because of this, this operation never fails.
return value

List of values corresponding to the specified key

example

redis> SET key1 "Hello"
OK
redis> SET key2 "World"
OK
redis> MGET key1 key2 nonexisting
1) "Hello"
2) "World"
3) (nil)
redis>

getrange

command
```
GETRANGE key start end
```
Description

Warning : This command is changed to GETRANGE, called SUBSTR in Redis version less than 2.0. Return the substring of the string value corresponding to the key. This substring is determined by the displacement of start and end (both are in the string). You can use a negative displacement to represent the subscript starting from the end of the string. So -1 is the last character, -2 is the second to last character, and so on.

When this function handles out-of-range requests, it limits the result to string.

example

redis> SET mykey "This is a string"
OK
redis> GETRANGE mykey 0 3
"This"
redis> GETRANGE mykey -3 -1
"ing"
redis> GETRANGE mykey 0 -1
"This is a string"
redis> GETRANGE mykey 10 100
"string"
redis>

strlen

command
```
STRLEN key
```
Description

Returns the length of the string value of the key. If the key corresponds to a non-string type, an error is returned.
return value

The length of the string value corresponding to the key, or 0 (the key does not exist)

example

redis> SET mykey "Hello world"
OK
redis> STRLEN mykey
(integer) 11
redis> STRLEN nonexisting
(integer) 0
redis>

append

command
```
APPEND key value
```
Description

If keyalready exists, and the value is a string, then the command will valuebe appended to the end of the original value (value) of. If keynot present, it will first create an empty string key, then perform additional operations, this situation APPEND will be similar to SET operation.
return value

Returns the length of the string value (value) after append.

example

redis> EXISTS mykey
(integer) 0
redis> APPEND mykey "Hello"
(integer) 5
redis> APPEND mykey " World"
(integer) 11
redis> GET mykey
"Hello World"
redis>

incr

command
```
INCR key
```
Description

keyPerform an atomic increment operation on the value stored in the specified value.

If the specified key does not exist, its value will be set to before performing the incr operation 0.

If the value stored in the specified key is not a string type (fix:) or the stored string type cannot be represented as an integer,

Then the server will return an error when executing this command (eq:(error) ERR value is not an integer or out of range).

This operation is limited to 64-bit signed integer data.

Note : Since redis does not have a clear type to represent integer data, this operation is a string operation.

When performing this operation, the stored string corresponding to the key is parsed into decimal 64-bit signed integer data .

In fact, Redis internally uses an integer representation to store the corresponding integer value, so this type of string value is actually stored as an integer, so there is no string representation for storing integers. Additional consumption.
return value

The keycorresponding value after the increment operation is performed .

example

redis> SET mykey "10"
OK
redis> INCR mykey
(integer) 11
redis> GET mykey
"11"
redis>

incrby

command
```
INCRBY key increment
```
Description

Add decrement to the number corresponding to the key. If the key does not exist, the key will be set to 0 before the operation. If the value type of the key is wrong or it is a string that cannot be represented as a number, an error is returned. This operation supports up to 64-bit signed positive numbers.

See the command INCR for additional information about the increase and decrease operations.
return value

The value after the increase.

example

redis> SET mykey "10"
OK
redis> INCRBY mykey 5
(integer) 15
redis>

incrbyfloat

command
```
INCRBYFLOAT key increment
```
Description

keyIncrease the value of a floating-point number (stored in a string) by specifying a floating-point number . When the key does not exist, first set its value to 0 before operating. Any of the following will return an error:
- The key contains an illegal value (not a string).
- The current key or the added value cannot be parsed as a double-precision floating point value (exceeding the precision range)
If the operation command is successful, the added value will replace the original value and store it on the corresponding key value, and return it in the type of string. The value stored in the string or the addition parameter can be arbitrarily selected with the exponential symbol, but the addition is calculated The result will be stored in the format of scientific notation. Regardless of the internal precision of each calculation, the output precision is fixed to 17 decimal places
return value

The current keyvalue after increment is increased.

example

redis> SET mykey 10.50
OK
redis> INCRBYFLOAT mykey 0.1
"10.6"
redis> SET mykey 5.0e3
OK
redis> INCRBYFLOAT mykey 2.0e2
"5200"
redis>

decr

command
```
DECR key
```
Description

Subtract 1 from the number corresponding to the key. If the key does not exist, the value corresponding to this key will be set to 0 before the operation. If the key has a value of the wrong type or a string that cannot be represented as a number, an error is returned. This operation supports up to 64-bit signed integer numbers.

See the command INCR for additional information about the increase and decrease operations.
return value

Value after reduction

example

redis> SET mykey "10"
OK
redis> DECR mykey
(integer) 9
redis> SET mykey "234293482390480948029348230948"
OK
redis> DECR mykey
ERR value is not an integer or out of range
redis>

decrby

command
```
DECRBY key decrement
```
Description

Decrement the number corresponding to the key. If the key does not exist, the key will be set to 0 before the operation. If the value type of the key is wrong or it is a string that cannot be represented as a number, an error is returned. This operation supports up to 64-bit signed positive numbers.

See the command INCR for additional information about the increase and decrease operations.
return value

Return a number: the value after the reduction.

example

redis> SET mykey "10"
OK
redis> DECRBY mykey 5
(integer) 5
redis>

of the

command
```
DEL key [key ...]
```
Description

Delete the specified batch of keys. If some keys in the deletion do not exist, they will be ignored.
return value

The number of deleted keys

example

redis> SET key1 "Hello"
OK
redis> SET key2 "World"
OK
redis> DEL key1 key2 key3
(integer) 2
redis>

Redis basic data type (string)

Redis basic data type (string)

Storage type

Common operation commands

set

get

mset

mget

getrange

strlen

append

incr

incrby

incrbyfloat

decr

decrby

of the

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