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110 lines
3.4 KiB
Markdown
110 lines
3.4 KiB
Markdown
---
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slug: /en/sql-reference/aggregate-functions/reference/argmax
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sidebar_position: 106
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---
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# argMax
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Calculates the `arg` value for a maximum `val` value. If there are several different values of `arg` for maximum values of `val`, returns the first of these values encountered.
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Both parts the `arg` and the `max` behave as [aggregate functions](/docs/en/sql-reference/aggregate-functions/index.md), they both [skip `Null`](/docs/en/sql-reference/aggregate-functions/index.md#null-processing) during processing and return not `Null` values if not `Null` values are available.
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**Syntax**
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``` sql
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argMax(arg, val)
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```
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**Arguments**
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- `arg` — Argument.
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- `val` — Value.
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**Returned value**
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- `arg` value that corresponds to maximum `val` value.
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Type: matches `arg` type.
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**Example**
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Input table:
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``` text
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┌─user─────┬─salary─┐
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│ director │ 5000 │
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│ manager │ 3000 │
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│ worker │ 1000 │
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└──────────┴────────┘
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```
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Query:
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``` sql
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SELECT argMax(user, salary) FROM salary;
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```
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Result:
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``` text
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┌─argMax(user, salary)─┐
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│ director │
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└──────────────────────┘
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```
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**Extended example**
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```sql
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CREATE TABLE test
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(
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a Nullable(String),
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b Nullable(Int64)
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)
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ENGINE = Memory AS
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SELECT *
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FROM VALUES(('a', 1), ('b', 2), ('c', 2), (NULL, 3), (NULL, NULL), ('d', NULL));
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select * from test;
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┌─a────┬────b─┐
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│ a │ 1 │
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│ b │ 2 │
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│ c │ 2 │
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│ ᴺᵁᴸᴸ │ 3 │
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│ ᴺᵁᴸᴸ │ ᴺᵁᴸᴸ │
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│ d │ ᴺᵁᴸᴸ │
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└──────┴──────┘
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SELECT argMax(a, b), max(b) FROM test;
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┌─argMax(a, b)─┬─max(b)─┐
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│ b │ 3 │ -- argMax = 'b' because it the first not Null value, max(b) is from another row!
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└──────────────┴────────┘
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SELECT argMax(tuple(a), b) FROM test;
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┌─argMax(tuple(a), b)─┐
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│ (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
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└─────────────────────┘
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SELECT (argMax((a, b), b) as t).1 argMaxA, t.2 argMaxB FROM test;
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┌─argMaxA─┬─argMaxB─┐
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│ ᴺᵁᴸᴸ │ 3 │ -- you can use Tuple and get both (all - tuple(*)) columns for the according max(b)
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└─────────┴─────────┘
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SELECT argMax(a, b), max(b) FROM test WHERE a IS NULL AND b IS NULL;
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┌─argMax(a, b)─┬─max(b)─┐
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│ 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`
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└──────────────┴────────┘
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SELECT argMax(a, (b,a)) FROM test;
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┌─argMax(a, tuple(b, a))─┐
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│ c │ -- There are two rows with b=2, `Tuple` in the `Max` allows to get not the first `arg`
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└────────────────────────┘
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SELECT argMax(a, tuple(b)) FROM test;
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┌─argMax(a, tuple(b))─┐
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│ b │ -- `Tuple` can be used in `Max` to not skip Nulls in `Max`
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└─────────────────────┘
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```
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**See also**
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- [Tuple](/docs/en/sql-reference/data-types/tuple.md)
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