问题
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 and not every kind of number. Is there such thing as ISINT or something?
Here is some code to make things clear. If MY_FIELD is not int, this code would fail:
SELECT @MY_VAR = CAST(MY_FIELD AS INT)
FROM MY_TABLE
WHERE MY_OTHER_FIELD = 'MY_FILTER'
Thank you
回答1:
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.
回答2:
In his article Can I convert this string to an integer?, Itzik Ben-Gan provides a solution in pure T-SQL and another that uses the CLR.
Which solution should you choose?
Is the T-SQL or CLR Solution Better? The advantage of using the T-SQL solution is that you don’t need to go outside the domain of T-SQL programming. However, the CLR solution has two important advantages: It's simpler and faster. When I tested both solutions against a table that had 1,000,000 rows, the CLR solution took two seconds, rather than seven seconds (for the T-SQL solution), to run on my laptop. So the next time you need to check whether a given string can be converted to an integer, you can include the T-SQL or CLR solution that I provided in this article.
If you only want to maintain T-SQL, then use the pure T-SQL solution. If performance is more important than convenience, then use the CLR solution.
The pure T-SQL Solution is tricky. It combines the built-in ISNUMERIC function with pattern-matching and casting to check if the string represents an int.
SELECT keycol, string, ISNUMERIC(string) AS is_numeric,
CASE
WHEN ISNUMERIC(string) = 0 THEN 0
WHEN string LIKE '%[^-+ 0-9]%' THEN 0
WHEN CAST(string AS NUMERIC(38, 0))
NOT BETWEEN -2147483648. AND 2147483647. THEN 0
ELSE 1
END AS is_int
FROM dbo.T1;
The T-SQL part of the CLR solution is simpler. You call the fn_IsInt function just like you would call ISNUMERIC.
SELECT keycol, string, ISNUMERIC(string) AS is_numeric,
dbo.fn_IsInt(string) AS is_int
FROM dbo.T1;
The C# part is simply a wrapper for the .NET's parsing function Int32.TryParse. This works because the SQL Server int and the .NET Int32 are both 32-bit signed integers.
using System;
using System.Data.SqlTypes;
public partial class UserDefinedFunctions
{
[Microsoft.SqlServer.Server.SqlFunction]
public static SqlBoolean fn_IsInt(SqlString s)
{
if (s.IsNull)
return SqlBoolean.False;
else
{
Int32 i = 0;
return Int32.TryParse(s.Value, out i);
}
}
};
Please read Itzik's article for a full explanation of these code samples.
回答3:
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
回答4:
WHERE IsNumeric(MY_FIELD) = 1 AND CAST(MY_FIELD as VARCHAR(5)) NOT LIKE '%.%'
That is probably the simplest solution. Unless your MY_FIELD contains .00 or something of that sort. In which case, cast it to a float to remove any trailing .00s
回答5:
See whether the below query will help
SELECT *
FROM MY_TABLE
WHERE CHARINDEX('.',MY_FIELD) = 0 AND CHARINDEX(',',MY_FIELD) = 0
AND ISNUMERIC(MY_FIELD) = 1 AND CONVERT(FLOAT,MY_FIELD) / 2147483647 <= 1
回答6:
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
回答7:
Necromancing.
As of SQL-Server 2012+, you can use TRY_CAST, which returns NULL if the cast wasn't successful.
Example:
DECLARE @foo varchar(200)
SET @foo = '0123'
-- SET @foo = '-0123'
-- SET @foo = '+0123'
-- SET @foo = '+-0123'
-- SET @foo = '+-0123'
-- SET @foo = '.123'
-- SET @foo = '1.23'
-- SET @foo = '.'
-- SET @foo = '..'
-- SET @foo = '0123e10'
SELECT CASE WHEN TRY_CAST(@foo AS integer) IS NULL AND @foo IS NOT NULL THEN 0 ELSE 1 END AS isInteger
This is the only really reliable way.
Should you need support for SQL-Server 2008, then fall back to Sam DeHaan's answer:
SELECT CASE WHEN ISNUMERIC(@foo + '.e0') = 1 THEN 1 ELSE 0 END AS isInteger
SQL-Server < 2012 (aka 2008R2) will reach end of (extended) support by 2019-07-09.
At this time, which is very soon, support for < 2012 can be dropped.
I wouldn't use any of the other hacks at this point in time anymore.
Just tell your frugal customers to update - it's been over 10 years since 2008.
回答8:
This work around with IsNumeric function will work:
select * from A where ISNUMERIC(x) =1 and X not like '%.%'
or Use
select * from A where x not like '%[^0-9]%'
回答9:
I think that there is something wrong with your database design. I think it is a really bad idea to mix varchar and numbers in one column? What is the reason for that?
Of course you can check if there are any chars other than [0-9], but imagine you have a 1m rows in table and your are checking every row. I think it won't work well.
Anyway if you really want to do it I suggest doing it on the client side.
回答10:
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
回答11:
I have a feeling doing it this way is the work of satan, but as an alternative:
How about a TRY - CATCH?
DECLARE @Converted as INT
DECLARE @IsNumeric BIT
BEGIN TRY
SET @Converted = cast(@ValueToCheck as int)
SET @IsNumeric=1
END TRY
BEGIN CATCH
SET @IsNumeric=0
END CATCH
select IIF(@IsNumeric=1,'Integer','Not integer') as IsInteger
This works, though only in SQL Server 2008 and up.
回答12:
Sometimes you don't get to design the database, you just have to work with what you are given. In my case it's a database located on a computer that I only have read access to which has been around since 2008.
I need to select from a column in a poorly designed database which is a varchar with numbers 1-100 but sometimes a random string. I used the following to get around it (although I wish I could have re designed the entire database).
SELECT A from TABLE where isnumeric(A)=1
回答13:
I am not a Pro in SQL but what about checking if it is devideable by 1 ? For me it does the job.
SELECT *
FROM table
WHERE fieldname % 1 = 0
回答14:
Use PATINDEX
DECLARE @input VARCHAR(10)='102030.40'
SELECT PATINDEX('%[^0-9]%',RTRIM(LTRIM(@input))) AS IsNumber
reference http://www.intellectsql.com/post-how-to-check-if-the-input-is-numeric/
回答15:
As of SQL Server 2012, the TRY_CONVERT and TRY_CAST functions were implemented. Thise are vast improvements over the ISNUMERIC solution, which can (and does) give false positives (or negatives). For example if you run the below:
SELECT CONVERT(int,V.S)
FROM (VALUES('1'),
('900'),
('hello'),
('12b'),
('1.1'),
('')) V(S)
WHERE ISNUMERIC(V.S) = 1;
Using TRY_CONVERT (or TRY_CAST) avoids that:
SELECT TRY_CONVERT(int,V.S),
V.S,
ISNUMERIC(V.S)
FROM (VALUES('1'),
('900'),
('hello'),
('12b'),
('1.1'),
('')) V(S)
--WHERE TRY_CONVERT(int,V.S) IS NOT NULL; --To filter to only convertable values
Notice that '1.1' returned NULL, which cause the error before (as a string represtation of a decimal cannot be converted to an int) but also that '' returned 0, even though ISNUMERIC states the value "can't be converted".
回答16:
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
回答17:
This works fine in SQL Server
SELECT (SELECT ISNUMERIC(2) WHERE ISNUMERIC(2)=1 AND 2 NOT LIKE '%.%')
来源：https://stackoverflow.com/questions/10517777/t-sql-determine-if-value-is-integer