Copy value from one table to another on matching IDs

[Anonymous]

I have a header and detail table that are linked by an unique ID. Both tables are imported from SQL server management studio. The header table has a column which I would like to add to the detail table. What would be the correct (and most efficient) way to copy this header column to the detail column considering the databases consists of a couple million rows. 

The header table looks like this (other columns have been left out of the example):

ID                                                                                                            Type

1	A
2	B

The detailed table should look like this: 
Type column is what I want to add to my table.

ID                                                                                                             Type

1	A
1	A
1	A
2	B
2	B

[ntaylo06]

A clarification question, are you adding "1" and "2" to the detailed table or "A" and "B"?

[Anonymous]

I would like to add the "Type" column to the detailed table. In the example that would be "A" and "B". 

[ntaylo06 · Accepted solution]

Gotcha, this one is pretty straightforward. I am using names that are different than yours for clarity, but this is how you will do it:

1. Create a relationship between 'Header_Table'[ID_Number] and 'Detail_Table'[ID_Number]

2. Add a column to 'Detail_Table' with the formula ID Number = RELATED('Header_Table'[Type])

Let me know if you have any questions.