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UNION vs UNION ALL, time to fetch first row

edited Sep 19, 2019 5:08AM in SQL Performance (MOSC) 7 commentsAnswered

It is obvious fact the UNION ALL is faster than UNION. If I measure the time to fetch first row, should the both UNION and UNION ALL should have same performance. That is because it does not need wait finish sorting as anyway it can show data in one data set?

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