diff --git a/pq/dup.sql b/pq/dup.sql
new file mode 100644
index 0000000..e125e5f
--- /dev/null
+++ b/pq/dup.sql
@@ -0,0 +1,17 @@
+SELECT
+    count(f.path) AS Cnt,
+    f.hash AS Hash,
+    array_agg(distinct i.path) Paths
+FROM
+    files AS f
+INNER JOIN
+    files i
+ON
+    i.hash = f.hash
+GROUP BY
+    f.hash
+HAVING
+    count(f.path)>1
+ORDER BY
+    Cnt DESC
+;