Question

here’s the situation, i have 3 tables that look like this.

table foo
type number
a    1
b    2
c    3
d    4

table bar
number shape
1      square
2      circle
3      triangle
4      rectangle

table foobar
shape     colour 
square    red
circle    green
triangle  blue
rectangle yellow
triangle  purple

they all also have unique ids that I have not listed.
I have type but I want to find colour. now I could do three SQL requests to get it but as the SQL is likely to be the bottleneck so I was wondering if I could combine the three SQL requests into one request.

Is it possible to do this and would it run faster than three separate SQL requests

1 would return red and 3 would return blue and purple.

Answer 1

SELECT fb.colour
FROM foo AS f
INNER JOIN bar AS b ON f.number = b.number
INNER JOIN foobar AS fb ON b.shape = fb.shape
WHERE f.type = "YOURTYPE"

You can use JOINS to join the rows and use a where clause to specify the type you want. It would definitely be faster then doing this:

SELECT number FROM foo WHERE type="YOURTYPE"
SELECT shape  FROM bar WHERE number="NUMBERRETRIEVEDFROM"
SELECT colour FROM foobar WHERE shape="SHAPE"