SQL Server导入平面文件时如何保留语音字符并解决查询无结果问题

Hey there! Let's sort out this frustrating issue where your accented characters are turning into those annoying diamond question marks after importing via SQL Server Management Studio's Import Flat File wizard. I’ve dealt with this dozens of times—here’s exactly what you need to do:

Why This Happens #

The diamond ? symbols mean your Unicode characters (like é, ö) are being converted to a single-byte encoding (think SQL_Latin1_General_CP1_CI_AS) that doesn’t support them. This usually stems from two key issues:

• Your table columns are using non-Unicode data types (like varchar instead of nvarchar)
• The import wizard is using the wrong encoding for your source file

Step-by-Step Fixes #

1. Switch Your Columns to Unicode Data Types #

First, make sure your table’s columns are set up to store Unicode characters. Non-Unicode types like varchar can only handle a limited set of characters—swap them for nvarchar (variable-length) or nchar (fixed-length):

• If you’re creating a new table:

  CREATE TABLE Temp (
      column1 NVARCHAR(255) NOT NULL,
      -- Add other columns with NVARCHAR/NCHAR as needed
  );
  

• If the table already exists, alter the column:

  ALTER TABLE Temp ALTER COLUMN column1 NVARCHAR(255);
  

Pro tip: Use NVARCHAR(MAX) for longer text instead of the legacy NTEXT type—it’s more flexible and supported in modern SQL Server versions.

2. Configure the Import Wizard Correctly #

When running the Import Flat File wizard, don’t skip the advanced settings—this is where you fix the encoding mismatch:

• After selecting your source file, proceed to the Advanced step (before previewing data)
• For each column that contains accented characters:
  • Set the Data Type to nvarchar (to match your table’s column type)
  • Check the Encoding dropdown at the top of the advanced window—select UTF-8 or Unicode (UTF-16) (whichever matches how your source file was saved)
• Finish the wizard, and your special characters should now import correctly

3. Query with the Unicode Prefix #

When searching for these characters, you need to tell SQL Server you’re using a Unicode string by adding the N prefix before your search term. Without it, SQL Server will convert your search string to non-Unicode, and you’ll get no results:

SELECT * FROM Temp WHERE column1 LIKE N'%é%';

The N stands for "National Character Set"—it ensures the string is treated as Unicode, matching your nvarchar column type.

4. Prevent This in the Future #

• Always use nvarchar/nchar for columns that might ever need to store non-ASCII characters (it’s safer than guessing you’ll never need them!)
• When exporting your source file (e.g., from Excel), choose UTF-8 encoding instead of the default ANSI—this preserves all special characters from the start

内容的提问来源于stack exchange，提问作者ssuhas76