BigQuery では COUNT(DISTINCT(X)) ではなく EXACT_COUNT_DISTINCT(X) を使おうBigQuery 以前、COUNT(DISTINCT(X)) の代わりに GROUP BY して COUNT(X) しようという記事を書きました。 BigQuery で COUNT(DISTINCT(X)) を使わない方が良い理由 が、今は時代が変わりました。BigQuery にいつの間にか、EXACT_COUNT_DISTINCT() 関数が追加されたのです! Returns the exact number of non-NULL, distinct values for the specified field. For better scalability and performance, use COUNT(DISTINCT field). さらに non
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