Question

I apologize if this is a dumb or simple question, and I have tried searching for it, but was unable to find a solution; I suspect I simply don’t know the name for this kind of an operation.

I have a MySQL database with a “card” table.

Cards have a casting cost, which may contain between 0 and 5 colors. I want to update every entry in the cards table to include 5 columns, each a boolean for each of the possible colors. So I would need a short algorithm which would parse the colors in a card, then populate the 5 boolean color values accordingly.

I can imagine how to do this with a PHP script, but I thought there must be some way to do it with pure MySQL. Am I mistaken, or is there a name for this type of script?

Answer 1

I understand your question to mean that your card table currently has a column called casting cost that contains a set of colours, e.g. 'red,green' or 'blue,orange,yellow' and that you are looking for a query that yields boolean columns indicating whether each possible colour is in the casting cost?

If so, MySQL’s FIND_IN_SET() function should give you what you’re after:

SELECT *,
       FIND_IN_SET('red',    `casting cost`) > 0 AS red,
       FIND_IN_SET('blue',   `casting cost`) > 0 AS blue,
       FIND_IN_SET('green',  `casting cost`) > 0 AS green,
       FIND_IN_SET('orange', `casting cost`) > 0 AS orange,
       FIND_IN_SET('yellow', `casting cost`) > 0 AS yellow
FROM   card

If you want to permanently change the table to include such columns:

ALTER TABLE card
  ADD COLUMN red    BOOLEAN NOT NULL DEFAULT FALSE,
  ADD COLUMN blue   BOOLEAN NOT NULL DEFAULT FALSE,
  ADD COLUMN green  BOOLEAN NOT NULL DEFAULT FALSE,
  ADD COLUMN orange BOOLEAN NOT NULL DEFAULT FALSE,
  ADD COLUMN yellow BOOLEAN NOT NULL DEFAULT FALSE

UPDATE card SET
  red    = FIND_IN_SET('red',    `casting cost`) > 0,
  blue   = FIND_IN_SET('blue',   `casting cost`) > 0,
  green  = FIND_IN_SET('green',  `casting cost`) > 0,
  orange = FIND_IN_SET('orange', `casting cost`) > 0,
  yellow = FIND_IN_SET('yellow', `casting cost`) > 0