MAX

Description

The MAX function returns the maximum non-NULL value of the expression.

Syntax

MAX(<expr>)

Parameters

Parameter	Description
<expr>	The expression to get the value. Supported types are String, Time, Date, DateTime, TimestampNs, Timestamptz, IPv4, IPv6, UUID, TinyInt, SmallInt, Integer, BigInt, LargeInt, Float, Double, Decimal, Array.

Return Value

Returns the same data type as the input expression. If all records in the group are NULL, the function returns NULL.

Behavior change (4.1.5)

In the Doris 4.1 series since 4.1.5, NULL elements inside complex values such as arrays compare greater than non-NULL elements at the same position. For example, [10, 20, NULL] is greater than [10, 20, 40]. This differs from an entire expression being NULL: those rows are still ignored. Before 4.1.5, aggregate comparisons treated NULL elements inside complex values as smaller.

Example

-- setup
create table t1(
        k1 int,
        k_string varchar(100),
        k_decimal decimal(10, 2),
        k_array array<int>
) distributed by hash (k1) buckets 1
properties ("replication_num"="1");
insert into t1 values 
    (1, 'apple', 10.01, [10, 20, 30]),
    (1, 'banana', 20.02, [10, 20]),
    (2, 'orange', 30.03, [10, 20, 40]),
    (2, null, null, [10, 20, null]),
    (3, null, null, null);

select k1, max(k_string) from t1 group by k1 order by k1;

For String type: Returns the maximum string value for each group.

+------+---------------+
| k1   | max(k_string) |
+------+---------------+
|    1 | banana        |
|    2 | orange        |
|    3 | NULL          |
+------+---------------+

select k1, max(k_decimal) from t1 group by k1 order by k1;

For Decimal type: Returns the maximum high-precision decimal value.

+------+----------------+
| k1   | max(k_decimal) |
+------+----------------+
|    1 |          20.02 |
|    2 |          30.03 |
|    3 |           NULL |
+------+----------------+

select k1, max(k_array) from t1 group by k1 order by k1;

For Array type: Compares elements in order and returns the maximum array value for each group. NULL elements compare greater than non-NULL elements at the same position.

+------+----------------+
| k1   | max(k_array)   |
+------+----------------+
|    1 | [10, 20, 30]   |
|    2 | [10, 20, null] |
|    3 | NULL           |
+------+----------------+

select max(k_string) from t1 where k1 = 3;

When all values in the group are NULL, returns NULL.

+---------------+
| max(k_string) |
+---------------+
| NULL          |
+---------------+

select max(k_string) from t1;

Returns the maximum value across all data.

+---------------+
| max(k_string) |
+---------------+
| orange        |
+---------------+