ClickHouse/docs/en/sql-reference/aggregate-functions/reference/argmin.md

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argMin

Calculates the arg value for a minimum val value. If there are multiple rows with equal val being the maximum, which of the associated arg is returned is not deterministic. Both parts the arg and the min behave as aggregate functions, they both skip Null during processing and return not Null values if not Null values are available.

Syntax

argMin(arg, val)

Arguments

• arg — Argument.
• val — Value.

Returned value

• arg value that corresponds to minimum val value.

Type: matches arg type.

Example

Input table:

┌─user─────┬─salary─┐
│ director │   5000 │
│ manager  │   3000 │
│ worker   │   1000 │
└──────────┴────────┘

Query:

SELECT argMin(user, salary) FROM salary

Result:

┌─argMin(user, salary)─┐
│ worker               │
└──────────────────────┘

Extended example

CREATE TABLE test
(
    a Nullable(String),
    b Nullable(Int64)
)
ENGINE = Memory AS
SELECT *
FROM VALUES((NULL, 0), ('a', 1), ('b', 2), ('c', 2), (NULL, NULL), ('d', NULL));

select * from test;
┌─a────┬────b─┐
│ ᴺᵁᴸᴸ │    0 │
│ a    │    1 │
│ b    │    2 │
│ c    │    2 │
│ ᴺᵁᴸᴸ │ ᴺᵁᴸᴸ │
│ d    │ ᴺᵁᴸᴸ │
└──────┴──────┘

SELECT argMin(a, b), min(b) FROM test;
┌─argMin(a, b)─┬─min(b)─┐
│ a            │      0 │ -- argMin = a because it the first not `NULL` value, min(b) is from another row!
└──────────────┴────────┘

SELECT argMin(tuple(a), b) FROM test;
┌─argMin(tuple(a), b)─┐
│ (NULL)              │ -- The a `Tuple` that contains only a `NULL` value is not `NULL`, so the aggregate functions won't skip that row because of that `NULL` value
└─────────────────────┘

SELECT (argMin((a, b), b) as t).1 argMinA, t.2 argMinB from test;
┌─argMinA─┬─argMinB─┐
│ ᴺᵁᴸᴸ    │       0 │ -- you can use `Tuple` and get both (all - tuple(*)) columns for the according max(b)
└─────────┴─────────┘

SELECT argMin(a, b), min(b) FROM test WHERE a IS NULL and b IS NULL;
┌─argMin(a, b)─┬─min(b)─┐
│ ᴺᵁᴸᴸ         │   ᴺᵁᴸᴸ │ -- All aggregated rows contains at least one `NULL` value because of the filter, so all rows are skipped, therefore the result will be `NULL`
└──────────────┴────────┘

SELECT argMin(a, (b, a)), min(tuple(b, a)) FROM test;
┌─argMin(a, tuple(b, a))─┬─min(tuple(b, a))─┐
│ d                      │ (NULL,NULL)      │ -- 'd' is the first not `NULL` value for the min
└────────────────────────┴──────────────────┘

SELECT argMin((a, b), (b, a)), min(tuple(b, a)) FROM test;
┌─argMin(tuple(a, b), tuple(b, a))─┬─min(tuple(b, a))─┐
│ (NULL,NULL)                      │ (NULL,NULL)      │ -- argMin returns (NULL,NULL) here because `Tuple` allows to don't skip `NULL` and min(tuple(b, a)) in this case is minimal value for this dataset
└──────────────────────────────────┴──────────────────┘

SELECT argMin(a, tuple(b)) FROM test;
┌─argMin(a, tuple(b))─┐
│ d                   │ -- `Tuple` can be used in `min` to not skip rows with `NULL` values as b.
└─────────────────────┘

See also

• Tuple