Data Types¶

This topic describes the data types that SQream DB supports, and how to convert between them.

In this topic:

Supported types
Converting and casting
Data type reference

Supported types ¶

Data types¶
Name	Description	Data size (not null, uncompressed)	Example
`BOOL`	Boolean values (`true`,``false``)	1 byte	`true`
`TINYINT`	Unsigned integer (0 - 255)	1 byte	`5`
`SMALLINT`	Integer (-32,768 - 32,767)	2 bytes	`-155`
`INT`	Integer (-2,147,483,648 - 2,147,483,647)	4 bytes	`1648813`
`BIGINT`	Integer (-9,223,372,036,854,775,808 - 9,223,372,036,854,775,807)	8 bytes	`36124441255243`
`REAL`	Floating point (inexact)	4 bytes	`3.141`
`DOUBLE` (`FLOAT`)	Floating point (inexact)	8 bytes	`0.000003`
`VARCHAR (n)`	Variable length string - ASCII only	`n` bytes	`'Kiwis have tiny wings, but cannot fly.'`
`NVARCHAR (n)`	Variable length string - UTF-8 unicode	Up to `4*n` bytes	`'キウイは楽しい鳥です'`
`DATE`	Date	4 bytes	`'1955-11-05'`
`DATETIME` (`TIMESTAMP`)	Date and time pairing in UTC	8 bytes	`'1955-11-05 01:24:00.000'`

Note

SQream DB compresses all columns and types. The data size noted is the maximum data size allocation for uncompressed data.

SQream DB supports explicit and implicit casting and type conversion. Implicit casts may be added automatically by the system when mixing different data types in the same expression. In many cases, the details of this are not important. However, these can affect the results of a query. When necessary, an explicit cast can be used to override the automatic cast added by SQream DB.

For example, the ANSI standard defines a SUM() aggregation over an INT column as an INT. However, when dealing with large amounts of data this could cause an overflow.

To rectify this, cast the value to a larger data type:

SUM(some_int_column :: BIGINT)

SQream DB supports three types of data conversion:

CAST(<value> TO <data type>), to convert a value from one type to another. For example, CAST('1997-01-01' TO DATE), CAST(3.45 TO SMALLINT), CAST(some_column TO VARCHAR(30)).
<value>::<data type>, a shorthand for the :ref:CAST syntax. For example, '1997-01-01' :: DATE, 3.45 :: SMALLINT, (3+5) :: BIGINT.
See the SQL functions reference for additional functions that convert from a specific value which is not an SQL type, such as FROM_UNIXTS, FROM_UNIXTSMS, etc.

Data type reference ¶

Boolean (`BOOL`)¶

A BOOL datatype is designed to store Boolean values of true or false.

Syntax¶

A BOOL type can accept either true or false (case insensitive).

When loading from CSV, BOOL columns can accept 0 as false and 1 as true.

Size¶

A BOOL type is 1 byte, but resulting average data sizes could be lower after compression.

Examples¶

CREATE TABLE animals (name VARCHAR(15), is_angry BOOL);

INSERT INTO animals VALUES ('fox',true), ('cat',true), ('kiwi',false);

SELECT name, CASE WHEN is_angry THEN 'Is really angry!' else 'Is not angry' END FROM animals;

"fox","Is really angry!"
"cat","Is really angry!"
"kiwi","Is not angry"

Casts and conversions¶

A BOOL value can be converted to:

Type	Details
`TINYINT`, `SMALLINT`, `INT`, `BIGINT`	`true` → `1`, `false` → `0`
`REAL`, `DOUBLE`	`true` → `1.0`, `false` → `0.0`

Integers (`TINYINT`, `SMALLINT`, `INT`, `BIGINT`)¶

Integer datatypes are designed to store whole numbers.

For information about identity sequences (sometimes called auto-increment or auto-numbers), see Identity (sequence).

Integer types¶

Integer types¶
Name	Details	Data size (not null, uncompressed)	Example
`TINYINT`	Unsigned integer (0 - 255)	1 byte	`5`
`SMALLINT`	Integer (-32,768 - 32,767)	2 bytes	`-155`
`INT`	Integer (-2,147,483,648 - 2,147,483,647)	4 bytes	`1648813`
`BIGINT`	Integer (-9,223,372,036,854,775,808 - 9,223,372,036,854,775,807)	8 bytes	`36124441255243`

Syntax¶

An integer can be entered as a regular literal, such as 12, -365.

Size¶

Integer types range between 1, 2, 4, and 8 bytes - but resulting average data sizes could be lower after compression.

Examples¶

CREATE TABLE cool_numbers (a INT NOT NULL, b TINYINT, c SMALLINT, d BIGINT);

INSERT INTO cool_numbers VALUES (1,2,3,4), (-5, 127, 32000, 45000000000);

SELECT * FROM cool_numbers;

1,2,3,4
-5,127,32000,45000000000

Casts and conversions¶

Integer values can be converted to:

Type	Details
`REAL`, `DOUBLE`	`1` → `1.0`, `-32` → `-32.0`
`VARCHAR(n)` (All numberic values must fit in the string length)	`1` → `'1'`, `2451` → `'2451'`

Floating point (`REAL`, `DOUBLE`)¶

REAL and DOUBLE are inexact floating point data types, designed to store up to 9 or 17 digits of precision respectively.

The floating point representation is based on IEEE 754.

Floating point types¶

Floating point types¶
Name	Details	Data size (not null, uncompressed)	Example
`REAL`	Single precision floating point (inexact)	4 bytes	`3.141`
`DOUBLE`	Double precision floating point (inexact)	8 bytes	`0.000003`

Aliases¶

DOUBLE is also known as FLOAT.

Syntax¶

A double precision floating point can be entered as a regular literal, such as 3.14, 2.718, .34, 2.71e-45.

To enter a REAL floating point number, cast the value. For example, (3.14 :: REAL).

Size¶

Floating point types are either 4 or 8 bytes, but size could be lower after compression.

Examples¶

CREATE TABLE cool_numbers (a REAL NOT NULL, b DOUBLE);

INSERT INTO cool_numbers VALUES (1,2), (3.14159265358979, 2.718281828459);

SELECT * FROM cool_numbers;

1.0,2.0
3.1415927,2.718281828459

Note

Most clients control display precision of floating point numbers, and values may appear differently in some clients.

Casts and conversions¶

Floating point values can be converted to:

Type	Details
`BOOL`	`1.0` → `true`, `0.0` → `false`
`TINYINT`, `SMALLINT`, `INT`, `BIGINT`	`2.0` → `2`, `3.14159265358979` → `3`, `2.718281828459` → `2`
`VARCHAR(n)` (n > 6 recommended)	`1` → `'1.0000'`, `3.14159265358979` → `'3.1416'`

String types (`VARCHAR`, `NVARCHAR`)¶

VARCHAR and NVARCHAR are types designed for storing text or strings of characters.

In this release, SQream DB separates ASCII (VARCHAR) and UTF-8 representations (NVARCHAR).

String types¶

String types¶
Name	Details	Data size (not null, uncompressed)	Example
`VARCHAR (n)`	Variable length string - ASCII only	`n` bytes	`'Kiwis have tiny wings, but cannot fly.'`
`NVARCHAR (n)`	Variable length string - UTF-8 unicode	Up to `4*n` bytes	`'キウイは楽しい鳥です'`

Length¶

Unlike some other types, the string types can be limited in length. To limit the length, use VARCHAR(n) or NVARCHAR(n), where n is the number of characters allowed.

If the data exceeds the column length limit on INSERT or COPY operations, SQream DB will return an error.
When casting or converting, the string has to fit in the target. For example, 'Kiwis are weird birds' :: VARCHAR(5) will return an error. Use SUBSTRING to truncate the length of the string.
VARCHAR strings are padded with spaces.

Syntax¶

String types can be written with standard SQL string literals, which are enclosed with single quotes, such as 'Kiwi bird'. To include a single quote in the string, repeat the quote twice: 'Kiwi bird''s wings are tiny'.

String literals can also be dollar-quoted with the dollar sign $. For example: $$Kiwi bird's wings are tiny$$ is the same as 'Kiwi bird''s wings are tiny'.

Size¶

VARCHAR(n) can occupy up to n bytes, whereas NVARCHAR(n) can occupy up to 4*n bytes. However, the size of strings is variable and is compressed by SQream DB.

Examples¶

CREATE TABLE cool_strings (a VARCHAR(25) NOT NULL, b NVARCHAR(40));

INSERT INTO cool_strings VALUES ('hello world', 'Hello to kiwi birds specifically');

INSERT INTO cool_strings VALUES ('This is ASCII only', 'But this column can contain 中文文字');

SELECT * FROM cool_strings;

hello world  ,Hello to kiwi birds specifically
This is ASCII only,But this column can contain 中文文字

Note

Most clients control display precision of floating point numbers, and values may appear differently in some clients.

Casts and conversions¶

String values can be converted to:

Type	Details
`BOOL`	`'true'` → `true`, `'false'` → `false`
`TINYINT`, `SMALLINT`, `INT`, `BIGINT`	`'2'` → `2`, `'-128'` → `-128`
`REAL`, `DOUBLE`	`'2.0'` → `2.0`, `'3.141592'` → `3.141592`
`DATE`, `DATETIME`	Requires a supported format, such as `'1955-11-05` → `date '1955-11-05'`, `'1955-11-05 01:24:00.000'` → `'1955-11-05 01:24:00.000'`

Date types (`DATE`, `DATETIME`)¶

DATE is a type designed for storing year, month, and day.

DATETIME is a type designed for storing year, month, day, hour, minute, seconds, and milliseconds in UTC with 1 millisecond precision.

Date types¶

Date types¶
Name	Details	Data size (not null, uncompressed)	Example
`DATE`	Date	4 bytes	`'1955-11-05'`
`DATETIME`	Date and time pairing in UTC	8 bytes	`'1955-11-05 01:24:00.000'`

Aliases¶

DATETIME is also known as TIMESTAMP.

Syntax¶

DATE values are formatted as string literals. For example, '1955-11-05' or date '1955-11-05'.

DATETIME values are formatted as string literals conforming to ISO 8601, for example '1955-11-05 01:26:00'.

SQream DB will attempt to guess if the string literal is a date or datetime based on context, for example when used in date-specific functions.

Size¶

A DATE column is 4 bytes in length, while a DATETIME column is 8 bytes in length.

However, the size of these values is compressed by SQream DB.

Examples¶

CREATE TABLE important_dates (a DATE, b DATETIME);

INSERT INTO important_dates VALUES ('1997-01-01', '1955-11-05 01:24');

SELECT * FROM important_dates;

1997-01-01,1955-11-05 01:24:00.0

SELECT a :: DATETIME, b :: DATE FROM important_dates;

1997-01-01 00:00:00.0,1955-11-05

Warning

Some client applications may alter the DATETIME value by modifying the timezone.

Casts and conversions¶

DATE and DATETIME values can be converted to:

Type	Details
`VARCHAR(n)`	`'1997-01-01'` → `'1997-01-01'`, `'1955-11-05 01:24'` → `'1955-11-05 01:24:00.000'`