The ROLLUP operator produces a summary of aggregates. This is useful when summary information is needed, but a full CUBE provides extraneous data or when you have sets within sets.是什么意思_The ROLLUP operator produces a summary of aggregates. This is useful when summary information is needed, but a full CUBE provides extraneous data or when you have sets within sets.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句