Categories:: Semi-structured and structured data functions (Array/Object)

ARRAY_TO_STRING¶

Returns an input array converted to a string by casting all values to strings (using TO_VARCHAR) and concatenating them (using the string from the second argument to separate the elements).

Syntax¶

ARRAY_TO_STRING( <array> , <separator_string> )

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Arguments¶

array: The array of elements to convert to a string.
separator_string: The string to put between each element, typically a space, comma, or other human-readable separator.

Returns¶

This function returns a value of type VARCHAR.

Usage notes¶

A NULL argument returns NULL as a result.
A NULL in an array is converted to an empty string in the result.
To include a blank space between values, you must precede the space with the separator character (e.g. ', '). See the examples below.

Examples¶

Return various arrays as concatenated strings:

SELECT column1,
       ARRAY_TO_STRING(PARSE_JSON(column1), '') AS no_separation,
       ARRAY_TO_STRING(PARSE_JSON(column1), ', ') AS comma_separated
  FROM VALUES
    (NULL),
    ('[]'),
    ('[1]'),
    ('[1, 2]'),
    ('[true, 1, -1.2e-3, "Abc", ["x","y"], {"a":1}]'),
    ('[, 1]'),
    ('[1, ]'),
    ('[1, , ,2]');

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+-----------------------------------------------+---------------------------------+-------------------------------------------+
| COLUMN1                                       | NO_SEPARATION                   | COMMA_SEPARATED                           |
|-----------------------------------------------+---------------------------------+-------------------------------------------|
| NULL                                          | NULL                            | NULL                                      |
| []                                            |                                 |                                           |
| [1]                                           | 1                               | 1                                         |
| [1, 2]                                        | 12                              | 1, 2                                      |
| [true, 1, -1.2e-3, "Abc", ["x","y"], {"a":1}] | true1-0.0012Abc["x","y"]{"a":1} | true, 1, -0.0012, Abc, ["x","y"], {"a":1} |
| [, 1]                                         | 1                               | , 1                                       |
| [1, ]                                         | 1                               | 1,                                        |
| [1, , ,2]                                     | 12                              | 1, , , 2                                  |
+-----------------------------------------------+---------------------------------+-------------------------------------------+

This example returns an array that contains a NULL value as a concatenated string. First, create a table and insert an array:

CREATE TABLE test_array_to_string_with_null(a ARRAY);

INSERT INTO test_array_to_string_with_null
  SELECT (['A', NULL, 'B']);

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Return the array as a concatenated string:

SELECT a,
       ARRAY_TO_STRING(a, ''),
       ARRAY_TO_STRING(a, ', ')
  FROM test_array_to_string_with_null;

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+--------------+------------------------+--------------------------+
| A            | ARRAY_TO_STRING(A, '') | ARRAY_TO_STRING(A, ', ') |
|--------------+------------------------+--------------------------|
| [            | AB                     | A, , B                   |
|   "A",       |                        |                          |
|   undefined, |                        |                          |
|   "B"        |                        |                          |
| ]            |                        |                          |
+--------------+------------------------+--------------------------+