Binaryworld - Check a string for numeric digits only ... [ SQL Server -> T-SQL ]

The ISNUMERIC function in SQL60/65/70 checks for decimal & integer values. Hence characters like D, E are valid float representations & similarly ','. This is a simple logic that can check only for numeric digits without using a loop of any kind.

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-- The numbers are hard-coded in the SELECT below but
-- use a NUMBERS table instead. This table can also be
-- used to solve several other problems quite easily.
declare @c varchar(10)
select @c = '12' + char(9)
if exists(select * from
(select 1 as digit union all select 2 union all
select 3 union all select 4 union all
select 5 union all select 6 union all
select 7 union all select 8 union all
select 9 union all select 10) as n
where ascii(substring(@c, digit, 1 )) not between 48 and 57 )
print 'No'
else
print 'Yes'

-- Or to check for unsigned integers alone
if patindex( '%[^0-9]%' , @c ) > 0
print 'No'
else
print 'Yes'