docs/UserGuide/Data-Concept/Data-Type.md

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# Data Type

## Basic Data Type

IoTDB supports the following data types:

* BOOLEAN (Boolean)
* INT32 (Integer)
* INT64 (Long Integer)
* FLOAT (Single Precision Floating Point)
* DOUBLE (Double Precision Floating Point)
* TEXT (String)

### Float Precision

The time series of **FLOAT** and **DOUBLE** type can specify (MAX\_POINT\_NUMBER, see [this page](../Reference/SQL-Reference.md) for more information on how to specify), which is the number of digits after the decimal point of the floating point number, if the encoding method is [RLE](Encoding.md) or [TS\_2DIFF](Encoding.md). If MAX\_POINT\_NUMBER is not specified, the system will use [float\_precision](../Reference/DataNode-Config-Manual.md) in the configuration file `iotdb-common.properties`.

```sql
CREATE TIMESERIES root.vehicle.d0.s0 WITH DATATYPE=FLOAT, ENCODING=RLE, 'MAX_POINT_NUMBER'='2';
```

* For Float data value, The data range is (-Integer.MAX_VALUE, Integer.MAX_VALUE), rather than Float.MAX_VALUE, and the max_point_number is 19, caused by the limition of function Math.round(float) in Java.
* For Double data value, The data range is (-Long.MAX_VALUE, Long.MAX_VALUE), rather than Double.MAX_VALUE, and the max_point_number is 19, caused by the limition of function Math.round(double) in Java (Long.MAX_VALUE=9.22E18).

### Data Type Compatibility

When the written data type is inconsistent with the data type of time-series,
- If the data type of time-series is not compatible with the written data type, the system will give an error message.
- If the data type of time-series is compatible with the written data type, the system will automatically convert the data type.

The compatibility of each data type is shown in the following table:

| Series Data Type | Supported Written Data Types |
|------------------|------------------------------|
| BOOLEAN          | BOOLEAN                      |
| INT32            | INT32                        |
| INT64            | INT32 INT64                  |
| FLOAT            | INT32 FLOAT                  |
| DOUBLE           | INT32 INT64 FLOAT DOUBLE     |
| TEXT             | TEXT                         |

## Timestamp

The timestamp is the time point at which data is produced. It includes absolute timestamps and relative timestamps

### Absolute timestamp

Absolute timestamps in IoTDB are divided into two types: LONG and DATETIME (including DATETIME-INPUT and DATETIME-DISPLAY). When a user inputs a timestamp, he can use a LONG type timestamp or a DATETIME-INPUT type timestamp, and the supported formats of the DATETIME-INPUT type timestamp are shown in the table below:

<div style="text-align: center;">

**Supported formats of DATETIME-INPUT type timestamp**



|            Format            |
| :--------------------------: |
|     yyyy-MM-dd HH:mm:ss      |
|     yyyy/MM/dd HH:mm:ss      |
|     yyyy.MM.dd HH:mm:ss      |
|    yyyy-MM-dd HH:mm:ssZZ     |
|    yyyy/MM/dd HH:mm:ssZZ     |
|    yyyy.MM.dd HH:mm:ssZZ     |
|   yyyy/MM/dd HH:mm:ss.SSS    |
|   yyyy-MM-dd HH:mm:ss.SSS    |
|   yyyy.MM.dd HH:mm:ss.SSS    |
|  yyyy-MM-dd HH:mm:ss.SSSZZ   |
|  yyyy/MM/dd HH:mm:ss.SSSZZ   |
|  yyyy.MM.dd HH:mm:ss.SSSZZ   |
| ISO8601 standard time format |

</div>


IoTDB can support LONG types and DATETIME-DISPLAY types when displaying timestamps. The DATETIME-DISPLAY type can support user-defined time formats. The syntax of the custom time format is shown in the table below:

<div style="text-align: center;">

**The syntax of the custom time format**


| Symbol |           Meaning           | Presentation |              Examples              |
| :----: | :-------------------------: | :----------: | :--------------------------------: |
|   G    |             era             |     era      |                era                 |
|   C    |    century of era (>=0)     |    number    |                 20                 |
|   Y    |      year of era (>=0)      |     year     |                1996                |
|        |                             |              |                                    |
|   x    |          weekyear           |     year     |                1996                |
|   w    |      week of weekyear       |    number    |                 27                 |
|   e    |         day of week         |    number    |                 2                  |
|   E    |         day of week         |     text     |            Tuesday; Tue            |
|        |                             |              |                                    |
|   y    |            year             |     year     |                1996                |
|   D    |         day of year         |    number    |                189                 |
|   M    |        month of year        |    month     |           July; Jul; 07            |
|   d    |        day of month         |    number    |                 10                 |
|        |                             |              |                                    |
|   a    |       halfday of day        |     text     |                 PM                 |
|   K    |   hour of halfday (0~11)    |    number    |                 0                  |
|   h    | clockhour of halfday (1~12) |    number    |                 12                 |
|        |                             |              |                                    |
|   H    |     hour of day (0~23)      |    number    |                 0                  |
|   k    |   clockhour of day (1~24)   |    number    |                 24                 |
|   m    |       minute of hour        |    number    |                 30                 |
|   s    |      second of minute       |    number    |                 55                 |
|   S    |     fraction of second      |    millis    |                978                 |
|        |                             |              |                                    |
|   z    |          time zone          |     text     |     Pacific Standard Time; PST     |
|   Z    |     time zone offset/id     |     zone     | -0800; -08:00; America/Los_Angeles |
|        |                             |              |                                    |
|   '    |       escape for text       |  delimiter   |                                    |
|   ''   |        single quote         |   literal    |                 '                  |

</div>

### Relative timestamp

Relative time refers to the time relative to the server time ```now()``` and ```DATETIME``` time.

 Syntax:

 ```
  Duration = (Digit+ ('Y'|'MO'|'W'|'D'|'H'|'M'|'S'|'MS'|'US'|'NS'))+
  RelativeTime = (now() | DATETIME) ((+|-) Duration)+
        
 ```

  <div style="text-align: center;">

**The syntax of the duration unit**


| Symbol |   Meaning   |       Presentation       | Examples |
| :----: | :---------: | :----------------------: | :------: |
|   y    |    year     |       1y=365 days        |    1y    |
|   mo   |    month    |       1mo=30 days        |   1mo    |
|   w    |    week     |        1w=7 days         |    1w    |
|   d    |     day     |         1d=1 day         |    1d    |
|        |             |                          |          |
|   h    |    hour     |     1h=3600 seconds      |    1h    |
|   m    |   minute    |      1m=60 seconds       |    1m    |
|   s    |   second    |       1s=1 second        |    1s    |
|        |             |                          |          |
|   ms   | millisecond | 1ms=1000_000 nanoseconds |   1ms    |
|   us   | microsecond |   1us=1000 nanoseconds   |   1us    |
|   ns   | nanosecond  |     1ns=1 nanosecond     |   1ns    |

  </div>

  eg：

  ```
  now() - 1d2h //1 day and 2 hours earlier than the current server time
  now() - 1w //1 week earlier than the current server time
  ```

  > Note：There must be spaces on the left and right of '+' and '-'.