Provide one-way or cryptographic hash functions, such as any of the MD5, SHA-1, SHA-2, or SHA-3 functions, so that views can define columns that are hashes of other columns.

The goal is to allow views to hide some columns (e.g., personally identifying information), but to expose a new "primary key" that is a hash of other existing columns. So, given this source table:

CREATE TABLE person (
  id INT PRIMARY KEY,
  name VARCHAR(256) NOT NULL,
  age INT,
  height INT,
  weight DOUBLE
);

a view could be created to hide the personally identifying information:

CREATE VIEW anonymousPerson ()
  id VARCHAR(64) PRIMARY KEY,
  age INT,
  height INT,
  weight DOUBLE
) AS
   SELECT sha256(p.id, p.name) AS id, 
          p.age AS age, 
          p.height AS height, 
          p.weight AS weight 
          FROM person AS p;