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

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sumWithOverflow

Computes the sum of the numbers, using the same data type for the result as for the input parameters. If the sum exceeds the maximum value for this data type, it is calculated with overflow.

Only works for numbers.

Syntax

sumWithOverflow(num)

Parameters

• num: Column of numeric values. (U)Int*, Float*, Decimal*.

Returned value

• The sum of the values. (U)Int*, Float*, Decimal*.

Example

First we create a table employees and insert some fictional employee data into it. For this example we will select salary as UInt16 such that a sum of these values may produce an overflow.

Query:

CREATE TABLE employees
(
    `id` UInt32,
    `name` String,
    `monthly_salary` UInt16
)
ENGINE = Log

SELECT
    sum(monthly_salary) AS no_overflow,
    sumWithOverflow(monthly_salary) AS overflow,
    toTypeName(no_overflow),
    toTypeName(overflow)
FROM employees

We query for the total amount of the employee salaries using the sum and sumWithOverflow functions and show their types using the toTypeName function. For the sum function the resulting type is UInt64, big enough to contain the sum, whilst for sumWithOverflow the resulting type remains as UInt16.

Query:

SELECT 
    sum(monthly_salary) AS no_overflow,
    sumWithOverflow(monthly_salary) AS overflow,
    toTypeName(no_overflow),
    toTypeName(overflow),    
FROM employees;

Result:

   ┌─no_overflow─┬─overflow─┬─toTypeName(no_overflow)─┬─toTypeName(overflow)─┐
1. │      118700 │    53164 │ UInt64                  │ UInt16               │
   └─────────────┴──────────┴─────────────────────────┴──────────────────────┘