first commit

lua-sqlite3-0.4.1/examples/aggregate.lua

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+
+require "path"
+require "sqlite3"
+
+
+local db = sqlite3.open_memory()
+
+assert( db:exec[[
+
+  CREATE TABLE test (col1, col2);
+
+  INSERT INTO test VALUES (1, 2);
+  INSERT INTO test VALUES (2, 4);
+  INSERT INTO test VALUES (3, 6);
+  INSERT INTO test VALUES (4, 8);
+  INSERT INTO test VALUES (5, 10);
+
+]] )
+
+
+assert( db:set_aggregate("my_stats", 2, function()
+
+  local square_error_sum = 0
+
+  local function step(a, b)
+    local error        = a - b
+    local square_error = error * error
+    square_error_sum   = square_error_sum + square_error
+  end
+
+  local function final(num_called)
+    return square_error_sum / num_called
+  end
+
+  return step, final
+
+end))
+
+
+local my_stats = db:first_cols("SELECT my_stats(col1, col2) FROM test")
+print("my_stats:", my_stats)