CODEWITHSUNDEEP
sqlsql-serversql-server-2005sql-server-2008types
jrara
jrara

Reputation: 16981

SQL Server: Is there a way to check what is the resulting data type of implicit conversion?

Is there a way to check what is the resulting data type of implicit conversion? Or do I simply have to know it based on data types joining the arithmetic operation?

declare @i as int
set @i = 3
select @i  / 9.0 as returning_numeric

Upvotes: 3

Views: 145

Answers (2)

Martin Smith
Martin Smith

Reputation: 452967

The result of the expression is numeric (17,6). To see this

DECLARE @i  INT, @v SQL_VARIANT

SET @i = 3
SET @v = @i  / 9.0

SELECT
    CAST(SQL_VARIANT_PROPERTY(@v, 'BaseType') AS VARCHAR(30)) AS BaseType,
    CAST(SQL_VARIANT_PROPERTY(@v, 'Precision') AS INT) AS Precision,
    CAST(SQL_VARIANT_PROPERTY(@v, 'Scale') AS INT) AS Scale

Returns

BaseType   Precision   Scale
---------- ----------- -----------
numeric    17          6

Edit:

SELECT SQL_VARIANT_PROPERTY(9.0, 'BaseType'),
       SQL_VARIANT_PROPERTY(9.0, 'Precision'),
       SQL_VARIANT_PROPERTY(9.0, 'Scale')

So the literal 9.0 is treated as numeric(2,1) (Can be seen from the query above)

@i is numeric(10,0) (as per Mikael's answer)

The rules that govern why numeric(10,0)/numeric(2,1) gives numeric (17,6) are covered here

Operation:        e1 / e2
Result precision: p1 - s1 + s2 + max(6, s1 + p2 + 1)
Result scale:     max(6, s1 + p2 + 1)

Substituting the relevant values in gives

10 - 0 + 1 + max(6, 0 + 2 + 1)  = 17
max(6, 0 + 2 + 1)               =  6

Upvotes: 3

Mikael Eriksson
Mikael Eriksson

Reputation: 138960

The implicit conversion done here is on @i to numeric(10,0). You can modify your statement and look at the execution plan.

declare @i int

set @i = 3
select @i  / 9.0
from (select 1) as x(x)

Extract from execution plan

<ScalarOperator ScalarString="CONVERT_IMPLICIT(numeric(10,0),[@i],0)/(9.0)">

However, the resulting data type is numeric(17,6) as Martin showed in his answer and that is not shown in the execution plan.

Upvotes: 2

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