PostgreSQL 18 reference · Array Functions

PostgreSQL ARRAY_TO_STRING() Function

Join array elements into a string with a separator, optionally writing NULLs as a given text.

PostgreSQL 18

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Syntax

array_to_string(array, delimiter, null_string)

Parameter	Description
`array`	An array value.
`delimiter`	The separator.
`null_string` optional	Text used for NULL elements; otherwise they're skipped.

text.

Join elements

SELECT array_to_string(ARRAY['a', 'b', 'c'], ', ') AS joined;

Output

 joined
---------
 a, b, c
(1 row)

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NULL elements

SELECT array_to_string(ARRAY['a', NULL, 'c'], '-') AS skip, array_to_string(ARRAY['a', NULL, 'c'], '-', '?') AS marked;

Output

 skip | marked
------+--------
 a-c  | a-?-c
(1 row)

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STRING_TO_ARRAY() · Split a string on a delimiter into a text array. A third argument turns matching fields into NULL.
STRING_AGG() · Join a group's non-NULL values into one string with a separator, optionally in a given ORDER BY order.
SQL String Functions · tutorial