能否一次性为整个SQL Server数据库启用Always Encrypted？

Hey there! Great question about Always Encrypted in SQL Server—let's dive right into this.

First things first: there’s no built-in way to enable Always Encrypted for an entire database in a single operation. This isn’t an oversight—it’s by design.

Always Encrypted is built as a column-level encryption mechanism, and here’s why that matters:

• It’s meant to protect specific sensitive columns (like SSNs, credit card numbers, or PII) rather than every piece of data in your database. Encrypting non-sensitive columns (e.g., timestamps, status codes) would add unnecessary performance overhead without any security benefit.
• Each encrypted column requires unique configuration tied to encryption keys (Column Master Keys and Column Encryption Keys). There’s no automated way to map these keys to every column across all tables in a database—you need to define which columns get which encryption settings.

While you can’t encrypt everything in one click, you can automate encryption for multiple columns across your database using T-SQL scripts. Here’s a step-by-step approach:

1. Identify Target Columns
   Use system views to filter columns that need encryption. For example, you might target columns with names indicating sensitive data, or specific data types:

   SELECT TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME, DATA_TYPE
   FROM INFORMATION_SCHEMA.COLUMNS
   WHERE 
       DATA_TYPE IN ('nvarchar', 'varchar', 'decimal', 'int') -- Adjust based on your data
       AND (COLUMN_NAME LIKE '%SSN%' OR COLUMN_NAME LIKE '%CreditCard%' OR COLUMN_NAME LIKE '%Email%') -- Match your sensitive column naming patterns
   

2. Generate Batch Encryption Scripts
   Use a cursor or dynamic SQL to loop through your target columns and generate ALTER TABLE statements. Here’s a working example:

   DECLARE @SchemaName NVARCHAR(128), @TableName NVARCHAR(128), @ColumnName NVARCHAR(128), @DataType NVARCHAR(128), @SQL NVARCHAR(MAX)
   DECLARE ColumnCursor CURSOR FOR
   SELECT TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME, 
          DATA_TYPE + CASE WHEN CHARACTER_MAXIMUM_LENGTH IS NOT NULL THEN '(' + CAST(CHARACTER_MAXIMUM_LENGTH AS NVARCHAR) + ')' ELSE '' END
   FROM INFORMATION_SCHEMA.COLUMNS
   WHERE 
       DATA_TYPE IN ('nvarchar', 'varchar')
       AND COLUMN_NAME LIKE '%SSN%'
   
   OPEN ColumnCursor
   FETCH NEXT FROM ColumnCursor INTO @SchemaName, @TableName, @ColumnName, @DataType
   WHILE @@FETCH_STATUS = 0
   BEGIN
       -- Build the ALTER TABLE statement (adjust encryption type and key name to match your setup)
       SET @SQL = N'ALTER TABLE ' + QUOTENAME(@SchemaName) + N'.' + QUOTENAME(@TableName) + 
                  N' ALTER COLUMN ' + QUOTENAME(@ColumnName) + N' ' + @DataType +
                  N' ENCRYPTED WITH (
                      ENCRYPTION_TYPE = DETERMINISTIC,
                      ALGORITHM = ''AEAD_AES_256_CBC_HMAC_SHA_256'',
                      COLUMN_ENCRYPTION_KEY = [Your_Column_Encryption_Key]
                  )'
       -- Execute the statement
       EXEC sp_executesql @SQL
       FETCH NEXT FROM ColumnCursor INTO @SchemaName, @TableName, @ColumnName, @DataType
   END
   CLOSE ColumnCursor
   DEALLOCATE ColumnCursor
   

3. Critical Pre-Execution Checks

   • Backup First: Always back up your database before modifying column encryption settings—mistakes can lead to data loss.
   • Low Traffic Window: Encrypting columns locks tables temporarily, so run this during off-peak hours.
   • App Compatibility: Ensure your application is configured to access the Always Encryption keys (via Azure Key Vault, a local key store, etc.)—otherwise, it won’t be able to read encrypted data.
   • Choose Encryption Type: Use DETERMINISTIC if you need to run equality queries on the column, or RANDOMIZED for stronger security (but no equality queries).

If your goal is to encrypt all data at rest (not just sensitive columns), Always Encrypted isn’t the right tool. Instead, consider:

• Transparent Data Encryption (TDE): Encrypts entire database files and logs at the storage level—completely transparent to applications, no code changes needed.
• Cell-Level Encryption: A different column-level encryption approach managed entirely within the SQL Server engine (unlike Always Encrypted’s client-side encryption).

内容的提问来源于stack exchange，提问作者Tom