Skip to main content

Data Types

Timestamp

When using TDengine to store and query data, the most important part of the data is timestamp. Timestamp must be specified when creating and inserting data rows. Timestamp must follow the rules below:

  • The format must be YYYY-MM-DD HH:mm:ss.MS, the default time precision is millisecond (ms), for example 2017-08-12 18:25:58.128.
  • Internal function NOW can be used to get the current timestamp on the client side.
  • The current timestamp of the client side is applied when NOW is used to insert data.
  • Epoch Time:timestamp can also be a long integer number, which means the number of seconds, milliseconds or nanoseconds, depending on the time precision, from UTC 1970-01-01 00:00:00.
  • Add/subtract operations can be carried out on timestamps. For example NOW-2h means 2 hours prior to the time at which query is executed. The units of time in operations can be b(nanosecond), u(microsecond), a(millisecond), s(second), m(minute), h(hour), d(day), or w(week). So SELECT * FROM t1 WHERE ts > NOW-2w AND ts <= NOW-1w means the data between two weeks ago and one week ago. The time unit can also be n (calendar month) or y (calendar year) when specifying the time window for down sampling operations.

Time precision in TDengine can be set by the PRECISION parameter when executing CREATE DATABASE. The default time precision is millisecond. In the statement below, the precision is set to nanonseconds.

CREATE DATABASE db_name PRECISION 'ns';

Data Types

In TDengine, the data types below can be used when specifying a column or tag.

#typeBytesDescription
1TIMESTAMP8Default precision is millisecond, microsecond and nanosecond are also supported.
2INT4Integer, the value range is [-2^31, 2^31-1].
3INT UNSIGNED4Unsigned integer, the value range is [0, 2^32-1].
4BIGINT8Long integer, the value range is [-2^63, 2^63-1].
5BIGINT UNSIGNED8unsigned long integer, the value range is [0, 2^64-1].
6FLOAT4Floating point number, the effective number of digits is 6-7, the value range is [-3.4E38, 3.4E38].
7DOUBLE8Double precision floating point number, the effective number of digits is 15-16, the value range is [-1.7E308, 1.7E308].
8BINARYUser DefinedSingle-byte string for ASCII visible characters. Length must be specified when defining a column or tag of binary type.
9SMALLINT2Short integer, the value range is [-32768, 32767].
10INT UNSIGNED2unsigned integer, the value range is [0, 65535].
11TINYINT1Single-byte integer, the value range is [-128, 127].
12TINYINT UNSIGNED1unsigned single-byte integer, the value range is [0, 255].
13BOOL1Bool, the value range is {true, false}.
14NCHARUser DefinedMulti-byte string that can include multi byte characters like Chinese characters. Each character of NCHAR type consumes 4 bytes storage. The string value should be quoted with single quotes. Literal single quote inside the string must be preceded with backslash, like \'. The length must be specified when defining a column or tag of NCHAR type, for example nchar(10) means it can store at most 10 characters of nchar type and will consume fixed storage of 40 bytes. An error will be reported if the string value exceeds the length defined.
15JSONJSON type can only be used on tags. A tag of json type is excluded with any other tags of any other type.
16VARCHARUser-definedAlias of BINARY
note
  • Only ASCII visible characters are suggested to be used in a column or tag of BINARY type. Multi-byte characters must be stored in NCHAR type.
  • The length of BINARY can be up to 16,374 bytes. The string value must be quoted with single quotes. You must specify a length in bytes for a BINARY value, for example binary(20) for up to twenty single-byte characters. If the data exceeds the specified length, an error will occur. The literal single quote inside the string must be preceded with back slash like \'
  • Numeric values in SQL statements will be determined as integer or float type according to whether there is decimal point or whether scientific notation is used, so attention must be paid to avoid overflow. For example, 9999999999999999999 will be considered as overflow because it exceeds the upper limit of long integer, but 9999999999999999999.0 will be considered as a legal float number.

Constants

TDengine supports a variety of constants:

#SyntaxTypeDescription
1[{+ | -}]123BIGINTInteger literals are of type BIGINT. Data that exceeds the length of the BIGINT type is truncated.
2123.45DOUBLEFloating-point literals are of type DOUBLE. Numeric values will be determined as integer or float type according to whether there is decimal point or whether scientific notation is used.
31.2E3DOUBLELiterals in scientific notation are of type DOUBLE.
4'abc'BINARYContent enclosed in single quotation marks is of type BINARY. The size of a BINARY is the size of the string in bytes. A literal single quote inside the string must be escaped with a backslash \'.
5'abc'BINARYContent enclosed in double quotation marks is of type BINARY. The size of a BINARY is the size of the string in bytes. A literal double quote inside the string must be escaped with a backslash \".
6TIMESTAMP {'literal' | "literal"}TIMESTAMPThe TIMESTAMP keyword indicates that the following string literal is interpreted as a timestamp. The string must be in YYYY-MM-DD HH:mm:ss.MS format. The precision is inherited from the database configuration.
7{TRUE | FALSE}BOOLBoolean literals are of type BOOL.
8{'' | "" | '\t' | "\t" | ' ' | " " | NULL }--The preceding characters indicate null literals. These can be used with any data type.
note

Numeric values will be determined as integer or float type according to whether there is decimal point or whether scientific notation is used, so attention must be paid to avoid overflow. For example, 9999999999999999999 will be considered as overflow because it exceeds the upper limit of long integer, but 9999999999999999999.0 will be considered as a legal float number.