-- 创建对称密钥  
CREATE MASTER KEY ENCRYPTION BY PASSWORD = '输入一个对称密钥';  -- 创建证书  
CREATE CERTIFICATE MyCertificate WITH SUBJECT = '创建一个证书名称';  -- 创建对称密钥的加密密钥  
CREATE SYMMETRIC KEY MySymmetricKey   WITH ALGORITHM = AES_128   ENCRYPTION BY CERTIFICATE MyCertificate;-- 打开对称密钥  
OPEN SYMMETRIC KEY MySymmetricKey   DECRYPTION BY CERTIFICATE MyCertificate;  -- 要加密的原始数据  
DECLARE @originalData VARCHAR(100) = 'Hello, World!';  -- 加密数据  
DECLARE @encryptedData VARBINARY(MAX);  
SET @encryptedData = ENCRYPTBYKEY(KEY_GUID('MySymmetricKey'), CAST(@originalData AS VARBINARY(MAX)));  -- 显示加密后的数据  
SELECT @encryptedData AS EncryptedData;  -- 解密数据  
DECLARE @decryptedData VARCHAR(100);  
SET @decryptedData = CAST(DECRYPTBYKEY(@encryptedData) AS VARCHAR(100));  -- 显示解密后的数据  
SELECT @decryptedData AS DecryptedData;  -- 关闭对称密钥  
CLOSE SYMMETRIC KEY MySymmetricKey;