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Functions

Function Syntax

function-name ( expr , )

Function Chaining via the Dot Operator

DuckDB supports the dot syntax for function chaining. This allows the function call fn(arg1, arg2, arg3, ...) to be rewritten as arg1.fn(arg2, arg3, ...). For example, take the following use of the replace function:

SELECT replace(goose_name, 'goose', 'duck') AS duck_name
FROM unnest(['African goose', 'Faroese goose', 'Hungarian goose', 'Pomeranian goose']) breed(goose_name);

This can be rewritten as follows:

SELECT goose_name.replace('goose', 'duck') AS duck_name
FROM unnest(['African goose', 'Faroese goose', 'Hungarian goose', 'Pomeranian goose']) breed(goose_name);

Tip

To apply function chaining to literals, you must use parentheses, e.g.:

SELECT ('hello world').replace(' ', '_');

Function chaining via the dot operator is limited to scalar functions; it is not available for table functions. For example, SELECT * FROM ('/myfile.parquet').read_parquet() is not supported.

Query Functions

The duckdb_functions() table function shows the list of functions currently built into the system.

SELECT DISTINCT ON(function_name)
    function_name,
    function_type,
    return_type,
    parameters,
    parameter_types,
    description
FROM duckdb_functions()
WHERE function_type = 'scalar'
  AND function_name LIKE 'b%'
ORDER BY function_name;
function_name function_type return_type parameters parameter_types description
bar scalar VARCHAR [x, min, max, width] [DOUBLE, DOUBLE, DOUBLE, DOUBLE] Draws a band whose width is proportional to (x - min) and equal to width characters when x = max. width defaults to 80
base64 scalar VARCHAR [blob] [BLOB] Convert a blob to a base64 encoded string
bin scalar VARCHAR [value] [VARCHAR] Converts the value to binary representation
bit_count scalar TINYINT [x] [TINYINT] Returns the number of bits that are set
bit_length scalar BIGINT [col0] [VARCHAR] NULL
bit_position scalar INTEGER [substring, bitstring] [BIT, BIT] Returns first starting index of the specified substring within bits, or zero if it is not present. The first (leftmost) bit is indexed 1
bitstring scalar BIT [bitstring, length] [VARCHAR, INTEGER] Pads the bitstring until the specified length

Currently, the description and parameter names of functions are not available in the duckdb_functions() function.

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