1 files changed, 30 insertions, 0 deletions
diff --git a/lib/sql/join.ml b/lib/sql/join.ml
new file mode 100644
index 0000000..3f82b92
--- /dev/null
+++ b/lib/sql/join.ml
@@ -0,0 +1,30 @@
+module D = Sqlite3.Data
+
+let f : Sqlite3.Data.t array -> Sqlite3.Data.t =
+ fun arguments ->
+  if Array.length arguments < 2 then Sqlite3.Data.NULL
+  else
+    let sep = Array.get arguments 0 in
+
+    (* Shift all the elements into an list*)
+    let contents =
+      Array.to_seqi arguments
+      |> Seq.filter_map (fun (i, value) ->
+             if i = 0 then None
+             else
+               match value with
+               | D.INT i -> Some (Int64.to_string i)
+               | D.FLOAT f -> Some (Float.to_string f)
+               | D.NONE -> None
+               | D.NULL -> None
+               | D.TEXT s | D.BLOB s ->
+                   if String.length s = 0 then None else Some (String.trim s))
+      |> List.of_seq
+    in
+
+    D.TEXT (String.concat (D.to_string_coerce sep) contents)
+
+let register : Sqlite3.db -> unit =
+ fun db ->
+  Sqlite3.create_funN db "join" f;
+  Sqlite3.create_funN db "concat" f