How to determine if NULL is contained in an array in Postgres?
select exists (
select 1
from unnest(array[1, null]) s(a)
where a is null
);
exists
--------
t
Or shorter:
select bool_or(a is null)
from unnest(array[1, null]) s(a)
;
bool_or
---------
t
Check if NULL exists in Postgres array
Postgres 9.5 or later
Or use array_position()
. Basically:
SELECT array_position(arr, NULL) IS NOT NULL AS array_has_null
See demo below.
Postgres 9.3 or later
You can test with the built-in functions array_remove()
or array_replace()
.
Postgres 9.1 or any version
If you know a single element that can never exist in your arrays, you can use this fast expression. Say, you have an array of positive numbers, and -1
can never be in it:
-1 = ANY(arr) IS NULL
Related answer with detailed explanation:
- Is array all NULLs in PostgreSQL
If you cannot be absolutely sure, you could fall back to one of the expensive but safe methods with unnest()
. Like:
(SELECT bool_or(x IS NULL) FROM unnest(arr) x)
or:
EXISTS (SELECT 1 FROM unnest(arr) x WHERE x IS NULL)
But you can have fast and safe with a CASE
expression. Use an unlikely number and fall back to the safe method if it should exist. You may want to treat the case arr IS NULL
separately. See demo below.
Demo
SELECT num, arr, expect
, -1 = ANY(arr) IS NULL AS t_1 -- 50 ms
, (SELECT bool_or(x IS NULL) FROM unnest(arr) x) AS t_2 -- 754 ms
, EXISTS (SELECT 1 FROM unnest(arr) x WHERE x IS NULL) AS t_3 -- 521 ms
, CASE -1 = ANY(arr)
WHEN FALSE THEN FALSE
WHEN TRUE THEN EXISTS (SELECT 1 FROM unnest(arr) x WHERE x IS NULL)
ELSE NULLIF(arr IS NOT NULL, FALSE) -- catch arr IS NULL -- 55 ms
-- ELSE TRUE -- simpler for columns defined NOT NULL -- 51 ms
END AS t_91
, array_replace(arr, NULL, 0) <> arr AS t_93a -- 99 ms
, array_remove(arr, NULL) <> arr AS t_93b -- 96 ms
, cardinality(array_remove(arr, NULL)) <> cardinality(arr) AS t_94 -- 81 ms
, COALESCE(array_position(arr, NULL::int), 0) > 0 AS t_95a -- 49 ms
, array_position(arr, NULL) IS NOT NULL AS t_95b -- 45 ms
, CASE WHEN arr IS NOT NULL
THEN array_position(arr, NULL) IS NOT NULL END AS t_95c -- 48 ms
FROM (
VALUES (1, '{1,2,NULL}'::int[], true) -- extended test case
, (2, '{-1,NULL,2}' , true)
, (3, '{NULL}' , true)
, (4, '{1,2,3}' , false)
, (5, '{-1,2,3}' , false)
, (6, NULL , null)
) t(num, arr, expect);
Result:
num | arr | expect | t_1 | t_2 | t_3 | t_91 | t_93a | t_93b | t_94 | t_95a | t_95b | t_95c
-----+-------------+--------+--------+------+-----+------+-------+-------+------+-------+-------+-------
1 | {1,2,NULL} | t | t | t | t | t | t | t | t | t | t | t
2 | {-1,NULL,2} | t | f --!! | t | t | t | t | t | t | t | t | t
3 | {NULL} | t | t | t | t | t | t | t | t | t | t | t
4 | {1,2,3} | f | f | f | f | f | f | f | f | f | f | f
5 | {-1,2,3} | f | f | f | f | f | f | f | f | f | f | f
6 | NULL | NULL | t --!! | NULL | f | NULL | NULL | NULL | NULL | f | f | NULL
Note that array_remove()
and array_position()
are not allowed for multi-dimensional arrays. All expressions to the right of t_93a
only work for 1-dimenstioal arrays.
db<>fiddle here - Postgres 13, with more tests
Old sqlfiddle
Benchmark setup
The added times are from a benchmark test with 200k rows in Postgres 9.5. This is my setup:
CREATE TABLE t AS
SELECT row_number() OVER() AS num
, array_agg(elem) AS arr
, bool_or(elem IS NULL) AS expected
FROM (
SELECT CASE WHEN random() > .95 THEN NULL ELSE g END AS elem -- 5% NULL VALUES
, count(*) FILTER (WHERE random() > .8)
OVER (ORDER BY g) AS grp -- avg 5 element per array
FROM generate_series (1, 1000000) g -- increase for big test case
) sub
GROUP BY grp;
Function wrapper
For repeated use, I would create a function in Postgres 9.5 like this:
CREATE OR REPLACE FUNCTION f_array_has_null (anyarray)
RETURNS bool
LANGUAGE sql IMMUTABLE PARALLEL SAFE AS
'SELECT array_position($1, NULL) IS NOT NULL';
PARALLEL SAFE
only for Postgres 9.6 or later.
Using a polymorphic input type this works for any array type, not just int[]
.
Make it IMMUTABLE
to allow performance optimization and index expressions.
- Does PostgreSQL support "accent insensitive" collations?
But don't make it STRICT
, which would disable "function inlining" and impair performance because array_position()
is not STRICT
itself. See:
- Function executes faster without STRICT modifier?
If you need to catch the case arr IS NULL
:
CREATE OR REPLACE FUNCTION f_array_has_null (anyarray)
RETURNS bool
LANGUAGE sql IMMUTABLE PARALLEL SAFE AS
'SELECT CASE WHEN $1 IS NOT NULL
THEN array_position($1, NULL) IS NOT NULL END';
For Postgres 9.1 use the t_91
expression from above. The rest applies unchanged.
Closely related:
- How to determine if NULL is contained in an array in Postgres?
Is array all NULLs in PostgreSQL
I think I got the shortest answer, while still preserving 4 = ALL (ARRAY[4,5]::integer[]);
construct:
Live test: https://www.db-fiddle.com/f/6DuB1N4FdcvZdxKiHczu5y/1
select
y, true = ALL (select unnest(z) is null)
from x
Check if value exists in Postgres array
Simpler with the ANY
construct:
SELECT value_variable = ANY ('{1,2,3}'::int[])
The right operand of ANY
(between parentheses) can either be a set (result of a subquery, for instance) or an array. There are several ways to use it:
- SQLAlchemy: how to filter on PgArray column types?
- IN vs ANY operator in PostgreSQL
Important difference: Array operators (<@
, @>
, &&
et al.) expect array types as operands and support GIN or GiST indices in the standard distribution of PostgreSQL, while the ANY
construct expects an element type as left operand and does not support these indices. Example:
- Index for finding an element in a JSON array
None of this works for NULL
elements. To test for NULL
:
- Check if NULL exists in Postgres array
How to check if an array is empty in Postgres
array_length()
requires two parameters, the second being the dimension of the array:
array_length(id_clients, 1) > 0
So:
IF array_length(id_clients, 1) > 0 THEN
query := query || format(' AND id = ANY(%L))', id_clients);
END IF;
This excludes both empty array and NULL.
Or use cardinality()
in Postgres 9.4 or later. See added answer by @bronzenose.
But if you're concatenating a query to run with EXECUTE
, it would be smarter to pass values with a USING
clause. Examples:
- Multirow subselect as parameter to `execute using`
- How to use EXECUTE FORMAT ... USING in postgres function
BTW, to explicitly check whether an array is empty (like your title says - but that's not what you need here) just compare it to an empty array:
id_clients = '{}'
That's all. You get:
TRUE
.. array is emptyNULL
.. array is NULLFALSE
.. any other case (array has elements - even if just NULL elements)
Postgres: array of NULL values
The engine can't infer the type of the array since all you have is NULLs there, and NULL can be of any type. So you'd somehow need to tell it it's a real NULL by casting it to real:
INSERT INTO test (id, depth_mm) VALUES (2, ARRAY[NULL::real,NULL,NULL]);
Or you can cast the entire array:
INSERT INTO test (id, depth_mm) VALUES (2, ARRAY[NULL,NULL,NULL]::real[]);
Stored procedure: how to check if NULL is present in postgresql array or not?
You can't use the ANY
operator to check for NULL values. You have to unnest the array and count the number of NULL elements:
if (select count(*) from unnest(user_zones_ids) as t(x) where x is null) > 0 then
... do something ...
end if;
Postgres: check if array field contains value?
This should work:
select * from mytable where 'Journal'=ANY(pub_types);
i.e. the syntax is <value> = ANY ( <array> )
. Also notice that string literals in postresql are written with single quotes.
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