在SQL Server中将varchar转换为nvarchar失败

Question

I have SQL Server table that contains columns of type varchar(50) as a result of a CSV import using the SQL Server Import wizard.

I was wanting to know how I can change this data type to nvarchar(9) without getting a SQL Server truncation error.

I tried doing a bulk update to set the data types and column sizes that I need but still had the truncation error message when I tried to load the csv into the empty database table I created (with my required data types that I need).

Grateful for any help.

Answer 1

Since you are willing to lose data and nvarchar will only be able to store 9 non-unicode charaters, then select only 9 characters from your source table, You do the truncation rather than Sql server doing it for you.

The Following Query will trim any White spaces from the strings, Then take only 9 characters from the string and convert them to NVARCHAR(9) for you.....

CREATE TABLE New_TABLE (Col1 NVARCHAR(9), Col2 NVARCHAR(9))
GO

INSERT INTO New_TABLE (Col1, Col2)
SELECT CONVERT(NVARCHAR(9),LEFT(LTRIM(Col1), 9))  
      ,CONVERT(NVARCHAR(9),LEFT(LTRIM(Col2), 9))
FROM Existing_Table
GO

Answer 2

Bulk insert into temp table with varchar(50) and insert to actual table

insert into tableName 
select cast(tempcolumn as nvarchar(9)) from temptable

Answer 3

And it is also important to check field types of destination table. Just spent 3 hours because of same error with random casting, trimming, substring and at the end noticed, that colleague created table with too short field lengths. I hope it helps somebody...

Answer 4

如果在导入/导出任务期间遇到此错误，则可以在“编写查询以指定要传输的数据”选项中将select cast(xxx as nvarchar(yyy)) as someName

Answer 5

varchar and nvarchar only use the length needed for the data stored. If you need unicode support certainly convert to nvarchar, but modifying it from 50 to 9 - what is the point?

If your data is ALWAYS exactly 9, consider using char(9), and following one of the transformation suggestions above...