问题
I need to checking a column where numeric or not in SQL Server 2012.
This my case code.
CASE
WHEN ISNUMERIC(CUST_TELE) = 1
THEN CUST_TELE
ELSE NULL
END AS CUSTOMER_CONTACT_NO
But when the '78603D99' value is reached, it returns 1 which means SQL Server considered this string as numeric.
Why is that?
How to avoid this kind of issues?
回答1:
Unfortunately, the ISNUMERIC() function in SQL Server has many quirks. It's not exactly buggy, but it rarely does what people expect it to when they first use it.
However, since you're using SQL Server 2012 you can use the TRY_PARSE() function which will do what you want.
This returns NULL:
SELECT TRY_PARSE('7860D399' AS int)
This returns 7860399
SELECT TRY_PARSE('7860399' AS int)
https://msdn.microsoft.com/en-us/library/hh213126.aspx
Obviously, this works for datatypes other than INT as well. You say you want to check that a value is numeric, but I think you mean INT.
回答2:
Although try_convert() or try_parse() works for a built-in type, it might not do exactly what you want. For instance, it might allow decimal points, negative signs, and limit the length of digits.
Also, isnumeric() is going to recognize negative numbers, decimals, and exponential notation.
If you want to test a string only for digits, then you can use not like logic:
(CASE WHEN CUST_TELE NOT LIKE '%[^0-9]%'
THEN CUST_TELE
END) AS CUSTOMER_CONTACT_NO
This simply says that CUST_TELE contains no characters that are not digits.
回答3:
Nothing substantive to add but a couple warnings.
1) ISNUMERIC() won't catch blanks but they will break numeric conversions.
2) If there is a single non-numeric character in the field and you use REPLACE to get rid of it you still need to handle the blank (usually with a CASE statement).
For instance if the field contains a single '-' character and you use this:
cast(REPLACE(myField, '-', '') as decimal(20,4)) myNumField
it will fail and you'll need to use something like this:
CASE WHEN myField IN ('','-') THEN NULL ELSE cast(REPLACE(myField, '-', '') as decimal(20,4)) END myNumField
来源：https://stackoverflow.com/questions/32135878/sql-servers-isnumeric-function