如何在SQL Server中将int转换或转换为字符串

Question

Looking at a column that holds last 4 of someone's SSN and the column was originally created as an int datatype. Now SSN that begin with 0 get registered as 0 on the database.

How can I convert the column and it's information from an int into a string for future proof?

Answer 1

You should convert. CONVERT(VARCHAR(4), your_col)

Answer 2

If you specifically want zero-padded numbers, then the simplest solution is format() :

select format(123, '0000')

If you want to fix the table, then do:

alter table t alter column ssn4 char(4);  -- there are always four digits

Then update the value to get the leading zeros:

update t
    ssn4 = format(convert(int, ssn4), '0000');

Or, if you just want downstream users to have the string, you can use a computed column:

alter table t
    add ssn4_str as (format(ssn4, '0000'));

Answer 3

如果要添加前导零，请使用：

SELECT RIGHT('0000'+ISNULL(SSN,''),4)

Answer 4

First thing never store SSN or Zip Code as any numeric type. Second you should fix the underlying table structure not rely on a conversion...but if you're in a jam this is an example of a case statement that will help you.

IF OBJECT_ID('tempdb..#t') IS NOT NULL
    BEGIN
        DROP TABLE #t
    END
GO
CREATE TABLE #t(
    LastFourSSN INT
)

INSERT INTO #t(LastFourSSN)
VALUES('0123'),('1234')

SELECT LastFourSSN --strips leading zero
FROM #t

SELECT -- adds leading zero to anything less than four charaters
    CASE 
        WHEN LEN(LastFourSSN) < 4 
        THEN '0' + CAST(LastFourSSN AS VARCHAR(3)) 
        ELSE CAST(LastFourSSN AS VARCHAR(4)) 
    END LastFourSSN 
FROM #t

Answer 5

If you are looking for converting values in the column for your purpose to use in application, you can use this following-

SELECT CAST(your_column AS VARCHAR(100))
--VARCHAR length based on your data

But if you are looking for change data type of your database column directly, you can try this-

ALTER TABLE TableName 
ALTER COLUMN your_column VARCHAR(200) NULL
--NULL or NOT NULL based on the data already stored in database