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

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maxMap

Calculates the maximum from value array according to the keys specified in the key array.

Syntax

maxMap(key, value)

or

maxMap(Tuple(key, value))

Alias: maxMappedArrays

:::note

• Passing a tuple of keys and value arrays is identical to passing two arrays of keys and values.
• The number of elements in key and value must be the same for each row that is totaled. :::

Parameters

• key — Array of keys. Array.
• value — Array of values. Array.

Returned value

• Returns a tuple of two arrays: keys in sorted order, and values calculated for the corresponding keys. Tuple(Array, Array).

Example

Query:

SELECT maxMap(a, b)
FROM values('a Array(Char), b Array(Int64)', (['x', 'y'], [2, 2]), (['y', 'z'], [3, 1]))

Result:

┌─maxMap(a, b)───────────┐
│ [['x','y','z'],[2,3,1]]│
└────────────────────────┘