How to convert Varchar column to Numeric - sql

Question

I have a requirement to move varchar column data to Numeric but with two conditions.
All the alphanumeric value should migrate as null
All the decimal values should go as it is.
I wrote the condition as WHERE data like '%[^0-9]%', it is working fine for all the records except for decimal.
Also I have values like .001 abcd, this has to be pass as null.
To summarize I need :
1) 1234 as 1234
2) 1.23 as 1.23
3) ABC as null
4) .ABC as null

Answer 1

There is by default function in SQL Server ISNUMERIC() so, first of all Check your data value by that function,
Select ISNUMERIC(DATA)
Whole query is written as below,
SELECT CASE WHEN ISNUMERIC(data)=1 THEN CAST(data as decimal(18,2))
ELSE NULL END as tData FROM DataTable
As per your question,first we have to convert with numeric with using case,which satisfies your first condition,another thing if the value is String than convert as NULL. In Above query both the condition has been taken care.
EDIT : If you are using SQL SERVER 2012 or higher version then use
TRY_PARSE(), then there will be no need to worry about using CASE too...
I have tried this,
SELECT TRY_PARSE('63.36' as decimal(18,2)) got result 63.36
and
SELECT TRY_PARSE('.' as decimal(18,2)) got result NULL

Answer 2

I think that this fits your spec. It is quite verbose, but hopefully it breaks down the conditions sufficiently that it's clearly doing the correct thing or, if it isn't, that it's easy enough to modify:
declare #t table (data varchar(30))
insert into #t(data) values
('1234'),
('1.23'),
('abc'),
('.abc'),
('+6000'),
('1.2.3')
select
CASE WHEN
Possible = 1 AND
(DecCheck = 0 OR
SingleDec = 1
) THEN
CONVERT(decimal(12,3),data)
END
from
#t t
cross apply
(select
--Only contains the correct characters
CASE WHEN not t.data like '%[^0-9.]%' THEN 1 ELSE 0 END as Possible,
--Contains a decimal point? (Needs more checks)
CASE WHEN CHARINDEX('.',t.data) > 0 THEN 1 ELSE 0 END as DecCheck,
CHARINDEX('.',t.data) as FirstDec --Where the first decimal point is
) p
cross apply
(select
CASE WHEN DecCheck = 1 THEN
--Only contains one decimal point
CASE WHEN LEN(data) = FirstDec + CHARINDEX('.',REVERSE(data)) - 1
THEN 1
ELSE 0 END
ELSE 0 END as SingleDec
) d
Results:
data
------------------------------ ---------------------------------------
1234 1234.000
1.23 1.230
abc NULL
.abc NULL
+6000 NULL
1.2.3 NULL
I.e. one additional check you may want to use is that a decimal cannot be the first or last character in the string. That is easy enough to do by adding those additional checks into the first CASE for the SingleDec column.

Answer 3

try ISNUMERIC function,
SELECT ISNUMERIC('abc')
SELECT ISNUMERIC('1.23')

Answer 4

On SQL Server (Version 2012, 11.0.5343)
SELECT
CASE WHEN ISNUMERIC('.') = 1 THEN <Field> ELSE 0 END
FROM
<Table>
works fine ...

Answer 5

Thre is A blog post.
Try following
SELECT
CASE
WHEN
ISNUMERIC(data + 'e0') = 1 THEN CAST(data AS decimal(18,2))
ELSE NULL END AS tData
FROM
DataTable

Answer 6

try ISNUMERIC function
DECLARE #MyTable TABLE(Val VARCHAR(100))
INSERT INTO #MyTable
VALUES
('1234')
,('1.23')
,('ABC')
,('.ABC')
,('MJA')
Select Val as OldValue,
Case
When ISNUMERIC(Val) = 1
then Cast(Val as numeric(18,2))
else null
end NewValue
From #MyTable
Output
OldValue NewValue
-----------------------------------------------------
1234 1234.00
1.23 1.23
ABC NULL
.ABC NULL
MJA NULL
(5 row(s) affected)