add example from issue #7

examples/NDT-server-iata-upload-download-union.md

@@ -0,0 +1,60 @@
+# NDT Upload and Download Tests to Servers in a specific Metro area identified by IATA code, over a defined time period.
+
+Tags:
+- unified views
+- geography
+- UUID matching
+- ndt5
+- tcpinfo
+- WITH
+- UNION
+- combined results
+
+The query below returns upload and download tests in a single table of results, limiting to tests conducted to M-Lab servers in a specific metro area. THe query uses the NDT "Helpful Views", _measurement-lab.ndt.unified_uploads_ and _measurement-lab.ndt.unified_downloads_, and matches the upload and download tests' UUIDs to limit tests to those within the metro area 'beg' using the field, `Server.IATA`, designating the airport code nearest to each M-Lab server. The query also includes some fields from the `ndt5` and `tcpinfo` tables by matching on each test's Universally Unique Identifier, or UUID.
+
+
+```~sql
+WITH
+dl AS (
+  SELECT
+    ndt.test_date AS test_date,
+    ndt.a.TestTime AS test_datetime,
+    EXTRACT(HOUR FROM a.TestTime) AS test_hour,
+    ndt.client.Geo.region AS region,
+    ndt.client.Geo.city AS city,
+    ndt.client.Geo.latitude AS client_latitude,
+    ndt.client.Geo.longitude AS client_longitude,
+    ndt.client.Network.ASNumber AS ASNumber,
+    a.MeanThroughputMbps AS mbps,
+    'download' AS test_type,
+    a.MinRTT AS MinRTT,
+    a.LossRate AS LossRate
+  FROM `measurement-lab.ndt.unified_downloads` ndt, `measurement-lab.ndt.tcpinfo` tcpinfo
+  WHERE 
+    a.UUID = tcpinfo.UUID
+    AND test_date >= '2020-01-01'
+    AND tcpinfo.Server.IATA = 'beg'
+),
+ul AS (
+  SELECT
+    ndt.test_date AS test_date,
+    ndt.a.TestTime AS test_datetime,
+    EXTRACT(HOUR FROM a.TestTime) AS test_hour,
+    ndt.client.Geo.region AS region,
+    ndt.client.Geo.city AS city,
+    ndt.client.Geo.latitude AS client_latitude,
+    ndt.client.Geo.longitude AS client_longitude,
+    ndt.client.Network.ASNumber AS ASNumber,
+    a.MeanThroughputMbps AS mbps,
+    'upload' AS test_type,
+    a.MinRTT AS MinRTT,
+    a.LossRate AS LossRate
+  FROM `measurement-lab.ndt.unified_uploads` ndt, `measurement-lab.ndt.tcpinfo` tcpinfo
+  WHERE 
+    a.UUID = tcpinfo.UUID
+    AND test_date >= '2020-01-01'
+    AND tcpinfo.Server.IATA = 'beg'
+)
+SELECT * FROM dl
+UNION ALL (SELECT * FROM ul)
+```