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Suppose we have three tables:

Table 1

|     c_id          |   categories     |   
|-------------------|------------------|
|      7            |       a          |     
|      4            |       b          |     
|      3            |       c          |

Table 2

|     c_id          |   dup_id     |   
|-------------------|--------------|
|       9           |     10       |     
|       5           |      3       |     
|       6           |      2       | ?

table 3

|     c_id          |  description |   
|-------------------|--------------|
|      22           |     xxxx     |     
|       5           |     yyyy     |     
|      11           |     zzzz     | ?

Suppose if some values ??in dup_id in Table1 are equal to dup_id in Table2, then we can find the dup_id# corresponding to dup_id ##, and use it to find description in Table3. What's the best way to do this?

Output:

|     c_id          |  description |   
|-------------------|--------------|    
|       5           |     yyyy     |