SELECT
  category,
  month,
  SUM(uah) dohod
FROM (
  SELECT
    LPAD(date, 6) month,
    product.productPrice * product.productQuantity uah,
    IF (product.productName ="Моторное масло", "maslo", IF (product.productName ="Аккумулятор", "akkum", "запчасти")) category
  FROM
    `dokdbroker.OWOXBI_Streaming.streaming_*`,
     UNNEST(product) product
  WHERE TRUE
    AND _TABLE_SUFFIX BETWEEN "20180401" AND "20180431"
    AND eCommerceAction.action_type = "purchase"
)
WHERE
  uah < 100000
GROUP BY
  category,
  month