Skip to content

Latest commit

 

History

History
193 lines (157 loc) · 8.12 KB

data-types.md

File metadata and controls

193 lines (157 loc) · 8.12 KB
Raw

Data Types

SQL data types define the type of data that a column can store. When you run the DESC TABLE command, you can see the data type of each column.

String and Binary Data Types

Type Name Description Size
String UTF-8 encoded strings. Holds up to 2,147,483,647 bytes of data The length of the strings
Binary Variable-length binary values. Holds up to 2,147,483,647 bytes of data The length of the data + 2 bytes

The maximum capacities of String and Binary are determined by their encodings and how the storage engine handles them. For example, String values are encoded into UTF-8. If all characters are 3 bytes in length, this field can store up to 715,827,882 characters. As for Binary types, they can store a maximum of 2,147,483,647 bytes.

Numeric Data Types

Type Name Description Size
Int8 -128 ~ 127 1 Byte
Int16 -32768 ~ 32767 2 Bytes
Int32 -2147483648 ~ 2147483647 4 Bytes
Int64 -9223372036854775808 ~ 9223372036854775807 8 Bytes
UInt8 0 ~ 255 1 Byte
UInt16 0 ~ 65535 2 Bytes
UInt32 0 ~ 4294967295 4 Bytes
UInt64 0 ~ 18446744073709551615 8 Bytes
Float32 32-bit IEEE754 floating point values 4 Bytes
Float64 Double precision IEEE 754 floating point values 8 Bytes

Decimal Type

GreptimeDB supports the decimal type, a fixed-point type represented as decimal(precision, scale), where precision is the total number of digits, and scale is the number of digits in the fractional part. For example, 123.45 has a precision of 5 and a scale of 2.

  • precision can range from [1, 38].
  • scale can range from [0, precision].

The default decimal is decimal(38, 10) if the precision and scale are not specified.

CREATE TABLE decimals(
    d DECIMAL(3, 2), 
    ts TIMESTAMP TIME INDEX,
);

INSERT INTO decimals VALUES ('0.1',1000), ('0.2',2000);

SELECT * FROM decimals;

Output:

+------+---------------------+
| d    | ts                  |
+------+---------------------+
| 0.10 | 1970-01-01T00:00:01 |
| 0.20 | 1970-01-01T00:00:02 |
+------+---------------------+

Date and Time Types

Type Name Description Size
TimestampSecond 64-bit timestamp values with seconds precision 8 Bytes
TimestampMillisecond 64-bit timestamp values with milliseconds precision 8 Bytes
TimestampMicroSecond 64-bit timestamp values with microseconds precision 8 Bytes
TimestampNanosecond 64-bit timestamp values with nanoseconds precision 8 Bytes

Boolean Type

Type Name Description Size
Boolean Bool values 1 Byte

Use TRUE or FALSE to represent boolean values in SQL statements. For example:

CREATE TABLE bools(
    b BOOLEAN, 
    ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP() TIME INDEX,
);
INSERT INTO bools(b) VALUES (TRUE), (FALSE);

Data types compatible with MySQL and PostgreSQL

Type aliases

For users migrating from MySQL or PostgreSQL to GreptimeDB, GreptimeDB supports the following alias types.

Data Type Alias Types
String Text, TinyText, MediumText, LongText, Varchar, Char
Binary Varbinary
Int8 TinyInt
Int16 SmallInt
Int32 Int
Int64 BigInt
UInt8 UnsignedInt
UInt16 UnsignedTinyInt
UInt32 UnsignedSmallInt
UInt64 UnsignedBigInt
Float32 Float
Float64 Double
TimestampSecond Timestamp_s, Timestamp_sec, Timestamp(0)
TimestampMillisecond Timestamp, Timestamp_ms, Timestamp(3)
TimestampMicroSecond Timestamp_us, Timestamp(6)
TimestampNanosecond Timestamp_ns, Timestamp(9)

You can use these alias types when creating tables. For example, use Varchar instead of String, Double instead of Float64, and Timestamp(0) instead of TimestampMillisecond.

CREATE TABLE alias_types (
  s TEXT,
  i DOUBLE,
  ts0 TIMESTAMP(0) DEFAULT CURRENT_TIMESTAMP() TIME INDEX,
  PRIMARY KEY(s)
);

Date and time types

In addition to the Timestamp types used as the default time type in GreptimeDB, GreptimeDB also supports Date and DateTime types for compatibility with MySQL and PostgreSQL.

Type name Description Size
Date 32-bit date values represent the days since UNIX Epoch 4 Bytes
DateTime 64-bit datetime values represent the milliseconds since UNIX Epoch 8 Bytes

Examples

Create Table

CREATE TABLE data_types (
  s STRING,
  vbi BINARY,
  b BOOLEAN,
  tint INT8,
  sint INT16,
  i INT32,
  bint INT64,
  utint UINT8,
  usint UINT16,
  ui UINT32,
  ubint UINT64,
  f FLOAT32,
  d FLOAT64,
  dm DECIMAL(3, 2), 
  dt DATE,
  dtt DATETIME,
  ts0 TIMESTAMPSECOND,
  ts3 TIMESTAMPMILLISECOND,
  ts6 TIMESTAMPMICROSECOND,
  ts9 TIMESTAMPNANOSECOND DEFAULT CURRENT_TIMESTAMP() TIME INDEX,
  PRIMARY KEY(s));

Describe Table

DESC TABLE data_types;
+--------+----------------------+------+------+---------------------+---------------+
| Column | Type                 | Key  | Null | Default             | Semantic Type |
+--------+----------------------+------+------+---------------------+---------------+
| s      | String               | PRI  | YES  |                     | TAG           |
| vbi    | Binary               |      | YES  |                     | FIELD         |
| b      | Boolean              |      | YES  |                     | FIELD         |
| tint   | Int8                 |      | YES  |                     | FIELD         |
| sint   | Int16                |      | YES  |                     | FIELD         |
| i      | Int32                |      | YES  |                     | FIELD         |
| bint   | Int64                |      | YES  |                     | FIELD         |
| utint  | UInt8                |      | YES  |                     | FIELD         |
| usint  | UInt16               |      | YES  |                     | FIELD         |
| ui     | UInt32               |      | YES  |                     | FIELD         |
| ubint  | UInt64               |      | YES  |                     | FIELD         |
| f      | Float32              |      | YES  |                     | FIELD         |
| d      | Float64              |      | YES  |                     | FIELD         |
| dm     | Decimal(3, 2)        |      | YES  |                     | FIELD         |
| dt     | Date                 |      | YES  |                     | FIELD         |
| dtt    | DateTime             |      | YES  |                     | FIELD         |
| ts0    | TimestampSecond      |      | YES  |                     | FIELD         |
| ts3    | TimestampMillisecond |      | YES  |                     | FIELD         |
| ts6    | TimestampMicrosecond |      | YES  |                     | FIELD         |
| ts9    | TimestampNanosecond  | PRI  | NO   | current_timestamp() | TIMESTAMP     |
+--------+----------------------+------+------+---------------------+---------------+