T-sql - determine if value is integer

Question

I want to determine if a value is integer (like TryParse in .NET). Unfortunatelly ISNUMERIC does not fit me because I want to parse only integers a

Answer 1

Use TRY_CONVERT which is an SQL alternative to TryParse in .NET. IsNumeric() isn’t aware that empty strings are counted as (integer)zero, and that some perfectly valid money symbols, by themselves, are not converted to (money)zero. reference

SELECT @MY_VAR = CASE WHEN TRY_CONVERT(INT,MY_FIELD) IS NOT NULL THEN MY_FIELD
                 ELSE 0
                 END
FROM MY_TABLE
WHERE MY_OTHER_FIELD = 'MY_FILTER'

Answer 2

Here's a blog post describing the creation of an IsInteger UDF.

Basically, it recommends adding '.e0' to the value and using IsNumeric. In this way, anything that already had a decimal point now has two decimal points, causing IsNumeric to be false, and anything already expressed in scientific notation is invalidated by the e0.

Answer 3

The following is correct for a WHERE clause; to make a function wrap it in CASE WHEN.

 ISNUMERIC(table.field) > 0 AND PATINDEX('%[^0123456789]%', table.field) = 0

Answer 4

declare @i numeric(28,5) = 12.0001


if (@i/cast(@i as int) > 1)
begin
    select 'this is not int'
end
else
begin
    select 'this is int'
end

Answer 5

With sqlserver 2005 and later you can use regex-like character classes with LIKE operator. See here.

To check if a string is a non-negative integer (it is a sequence of decimal digits) you can test that it doesn't contain other characters.

SELECT numstr
  FROM table
 WHERE numstr NOT LIKE '%[^0-9]%'

Note1: This will return empty strings too.

Note2: Using LIKE '%[0-9]%' will return any string that contains at least a digit.

See fiddle

Answer 6

Why not just do something like:

CASE
WHEN ROUND(MY_FIELD,0)=MY_FIELD THEN CAST(MY_FIELD AS INT)
ELSE MY_FIELD
END
as MY_FIELD2