Data Types
General-Purpose Data Types
The table below shows all the built-in general-purpose data types. The alternatives listed in the aliases column can be used to refer to these types as well, however, note that the aliases are not part of the SQL standard and hence might not be accepted by other database engines.
| Name | Aliases | Description |
|---|---|---|
BIGINT | INT8, LONG | signed eight-byte integer |
BIT | BITSTRING | string of 1's and 0's |
BOOLEAN | BOOL, LOGICAL | logical boolean (true/false) |
BLOB | BYTEA, BINARY, VARBINARY | variable-length binary data |
DATE | calendar date (year, month day) | |
DOUBLE | FLOAT8, NUMERIC, DECIMAL | double precision floating-point number (8 bytes) |
DECIMAL(prec, scale) | fixed-precision number with the given width (precision) and scale | |
HUGEINT | signed sixteen-byte integer | |
INTEGER | INT4, INT, SIGNED | signed four-byte integer |
INTERVAL | date / time delta | |
REAL | FLOAT4, FLOAT | single precision floating-point number (4 bytes) |
SMALLINT | INT2, SHORT | signed two-byte integer |
TIME | time of day (no time zone) | |
TIMESTAMP | DATETIME | combination of time and date |
TIMESTAMP WITH TIME ZONE | TIMESTAMPTZ | combination of time and date that uses the current time zone |
TINYINT | INT1 | signed one-byte integer |
UBIGINT | unsigned eight-byte integer | |
UINTEGER | unsigned four-byte integer | |
USMALLINT | unsigned two-byte integer | |
UTINYINT | unsigned one-byte integer | |
UUID | UUID data type | |
VARCHAR | CHAR, BPCHAR, TEXT, STRING | variable-length character string |
Nested / Composite Types
DuckDB supports four nested data types: LIST, STRUCT, MAP and UNION. Each supports different use cases and has a different structure.
| Name | Description | Rules when used in a column | Build from values | Define in DDL/CREATE |
|---|---|---|---|---|
| LIST | An ordered sequence of data values of the same type. | Each row must have the same data type within each LIST, but can have any number of elements. | [1, 2, 3] | INT[ ] |
| STRUCT | A dictionary of multiple named values, where each key is a string, but the value can be a different type for each key. | Each row must have the same keys. | {'i': 42, 'j': 'a'} | STRUCT(i INT, j VARCHAR) |
| MAP | A dictionary of multiple named values, each key having the same type and each value having the same type. Keys and values can be any type and can be different types from one another. | Rows may have different keys. | map([1,2],['a','b']) | MAP(INT, VARCHAR) |
| UNION | A union of multiple alternative data types, storing one of them in each value at a time. A union also contains a discriminator "tag" value to inspect and access the currently set member type. | Rows may be set to different member types of the union. | union_value(num := 2) | UNION(num INT, text VARCHAR) |
Nesting
LISTs, STRUCTs, MAPs and UNIONs can be arbitrarily nested to any depth, so long as the type rules are observed.
-- Struct with lists
SELECT {'birds': ['duck', 'goose', 'heron'], 'aliens': NULL, 'amphibians': ['frog', 'toad']};
-- Struct with list of maps
SELECT {'test': [map([1, 5], [42.1, 45]), map([1, 5], [42.1, 45])]};
-- A list of unions
SELECT [union_value(num := 2), union_value(str := 'ABC')::UNION(str VARCHAR, num INTEGER)];