Question

I have 2 tables that I need to join and select the unique rows from. Here is a sample of my data: (there are more columns)

tbl1:
MB# MBName  PCCNo_PRI   Primary_IP       PCCNo_SEC          Secondary_IP    ID
100  name    0               10.1.9.10       30              10.1.9.10       1 
103  name3   17              10.1.9.27       47              10.1.9.67       4
403  name13  17              10.1.9.27       47              10.1.9.67       14

tbl2:

RTU PCC#_PRI    PCC#_SEC    STATION ADDRESS
15  0           30          6
52  12          42          1
53* 17          47          1
54  18          48          1
63  9           39          2
69* 17          47          2

I need to join the two tables and get the unique RTU(s) in tbl2 for a given MB# in tbl1.
Query =

SELECT t1.MB#,t2.RTU,t2.[Device Manufacturer],t2.PCC#_PRI,t2.PCC#_SEC,t2.[STATION ADDRESS] 
INTO C300_RTU_MASTERBLK_Map
FROM mbm_PCDIMasterBlk_tbl as t1, dbo.WOA_PCC_Conn_tbl as t2
WHERE t1.PCCNo_PRI = t2.PCC#_PRI

I am getting duplicate rows for tbl2 53 and 69 (* above). 53 ends up with 2 entries; one to 103 and one 403 (69 gets same). How can I query this for unique RTU(s) to MB#?

Answer 1

The duplicate rows appears because you join on “17” which gives 2 rows on each side

Then, as it stands, you can’t with that SELECT list.
How do you decide which t1.MB# you want for the t2 columns?

There is no secondary JOIN column that I can see.
So the best you can get is use MAX (or MIN) to pick either 403 or 103.

SELECT
   MAX(t1.MB#) AS MB#,
   t2.RTU,t2.[Device Manufacturer],t2.PCC#_PRI,t2.PCC#_SEC,t2.[STATION ADDRESS] 
INTO C300_RTU_MASTERBLK_Map
FROM 
   dbombm_PCDIMasterBlk_tbl as t1
   JOIN
   dbo.WOA_PCC_Conn_tbl as t2 ON t1.PCCNo_PRI = t2.PCC#_PRI
GROUP BY
   t2.RTU,t2.[Device Manufacturer],t2.PCC#_PRI,t2.PCC#_SEC,t2.[STATION ADDRESS]