I recently had a requirement to load some data from a source table to another destination table. The destination columns were exactly the same as the source columns with the same data types and length. The only difference was that some columns on the destination table must be encrypted. The task was to use the SHA2_512 encryption algorithm to encrypt the “sensitive” data. I will talk more about the encryption algorithm in another post.
To achieve this, I needed to use the HASHBYTES function in SQL Server. The challenge was that this function used with the SHA2_512 encryption algorithm will return a fixed character length of 64 characters which will be longer than the character length on my destination table. As a result, SQL Server will throw a truncation error. I will demonstrate this below.
One really important point: SHA is not encryption; it’s a hash (which is why the function is
HASHBYTES() instead of something like
EncryptByKey() as column-level security uses). Hashes are intended to be a one-way trip, whereas encryption implies an ability to decrypt if you have the relevant key details. Here, the use looks to be obfuscating the text of sensitive data fields, perhaps for loading in a dev/test environment, and so the actions themselves are quite reasonable.
By the way, the styles Abayomi talks about are all listed in this Docs page. Turns out that if you’re using a
money datatype, you can use
CONVERT() to display the end result with commas.