How to prevent arithmetic overflow error when using SUM on INT column?

问题

I am using SQL Server 2008 R2 and I have an INT column where the data inserted never surpasses the max INT, but I have a query which uses the SUM function which when executed surpasses the max INT limit and throws the error mentioned in the title.

I want to be able to execute this query without changing the column type from INT to BIGINT.

Here is my query:

SELECT    UserId,
          SUM( PokemonExp )     AS TotalExp,
          MAX( PokemonLevel )   AS MaxPokeLevel

FROM      mytable

GROUP BY  UserId
ORDER BY  TotalExp DESC

Note: The PokemonExp column is of type INT.

回答1:

Type of expression in SUM determines return type.

Try the following:

SELECT    UserId,
          SUM( CAST( PokemonExp AS BIGINT ))  AS TotalExp,
          MAX( PokemonLevel )                 AS MaxPokeLevel

FROM      mytable

GROUP BY  UserId
ORDER BY  TotalExp DESC

回答2:

You don't have to change the column type to BIGINT to get a proper sum.

Just CAST or CONVERT PokemonExp to BIGINT before you perform the SUM like follows:

SUM( CAST( PokemonExp AS BIGINT ))

回答3:

Accepted type of expression in SUM determines return type.

Try the following:

SELECT    UserId,
          SUM( CAST( PokemonExp AS BIGINT ))  AS TotalExp,
          MAX( PokemonLevel )                 AS MaxPokeLevel

FROM      mytable

GROUP BY  UserId
ORDER BY  TotalExp DESC

来源：https://stackoverflow.com/questions/8289310/how-to-prevent-arithmetic-overflow-error-when-using-sum-on-int-column