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Il 98% dei viaggiatori non riconosce le banconote locali
The maximum number of unique for a given group. The number of unique objects for that group is calculated. This method allows for estimating unique counts for multiple groupings, reducing the overall query time. For example, if you have a table of customer transactions, you might want to know how many unique products each customer bought, how many unique customers visited each store, and how many unique products were sold in each region. Instead of running three separate COUNT(DISTINCT …) queries, you can run one `estimate_distinct_count_for_multiple_groups` query. **Parameters:** * `table_name`: The name of the table to query. * `group_by_columns`: A list of column names to group by. Each element in the list can be either a string (representing a single column) or a tuple of strings (representing multiple columns that should be treated as a single grouping unit). * `count_distinct_column`: The name of the column for which to count distinct values within each group. * `error_rate`: (Optional) The desired error rate for the HyperLogLog++ algorithm. This value should be between 0 and 1. A smaller error rate results in more accurate estimates but may require more memory. Defaults to 0.01. **Returns:** A list of dictionaries, where each dictionary represents a grouping and contains the following keys: * `group_by_key`: A string representation of the column(s) used for grouping. * `estimated_distinct_count`: The estimated number of distinct values for the `count_distinct_column` within that group. **Example Usage:** python from google.cloud import bigquery client = bigquery.Client() # Example table with customer transactions table_id =
