Question

I am using SQL Server.

I have a table item_table like this:

item   age
--------------    
1      1 
1      6 
2      2    

I have the other table price_table like this:

item    pricetype    price
--------------------------    
1       O             5
1       P             6
1       V             7
2       O             8
2       P             9
2       V             10

So, I want to inner join above two tables.

select *
from item_table i
inner join price_table p
on ...

There are some conditions about the on:

1. if the average of age of an item is bigger than 3, then I do: inner join price_table on pricetype = 'O' or pricetype = 'P'
2. If not, then I do: inner join price_table on pricetype = 'O' or pricetype = 'P' or pricetype = 'V'

So there are conditions for on conditions.

How can I write the select query?

Edit:
I changed the condition to be average of age, instead of type

Answer 1

select i.item, i.type, p.pricetype, p.price
from item_table i
inner join price_table p on i.item = p.item 
    and (i.type = 1 and p.pricetype in ('O', 'P'))
        or (i.type = 2 and p.pricetype in ('O', 'P', 'V'))

SQL Fiddle Example

Output:

| ITEM | TYPE | PRICETYPE | PRICE |
-----------------------------------
|    1 |    1 |         O |     5 |
|    1 |    1 |         P |     6 |
|    2 |    2 |         O |     5 |
|    2 |    2 |         P |     6 |
|    2 |    2 |         V |     7 |
|    2 |    2 |         O |     8 |
|    2 |    2 |         P |     9 |
|    2 |    2 |         V |    10 |