Question

Given the following example:

fav_colors
-----------------------
id   col1   col2   col3
-----------------------
01    01     03     03
02    04     02     01
03    01     03     02

colors
-----------
id   colors
-----------
01   green
02   red
03   blue
04   orange

What kind of SELECT statement works to pull the string values from colors for all 3 colors of a particular ID in the fav_colors table?

Something like:

SELECT col1, col2, col3
FROM fav_colors
INNER JOIN ?
WHERE fc.id = 03;

I’m guessing a fav_color array would make this easier, but am relying on these values being separate columns. How do you join the same table to multiple columns in another table?

Edit: All the answers below technically work. Agree that if relying heavily on multiple color info, you’re better off recording each color as a referenced row in fav_colors. Thanks!

Answer 1

Table aliases…

SELECT fc.id, fc.col1, c1.colors, fc.col2, c2.colors, fc.col3, c3.colors
  FROM fav_colors AS fc
  JOIN colors AS c1 ON fc.col1 = c1.id
  JOIN colors AS c2 ON fc.col2 = c2.id
  JOIN colors AS c3 ON fc.col3 = c3.id
 WHERE fc.id = 03;

Ideally, you’d have a fav_colors table more like:

CREATE TABLE fav_colors
(
    id    INTEGER NOT NULL REFERENCES Users, -- Hypothetical table defining id values
    seq   INTEGER NOT NULL CHECK(seq BETWEEN 1 AND 3),
    color INTEGER NOT NULL REFERENCES Colors
    PRIMARY KEY(id, seq)
);

You might have to tweak some of that syntax for your particular DBMS.