Shulou(Shulou.com)06/01 Report--

Today, in the implementation of business, it is found that the frequent use of contains statements is inefficient and does not produce results at all, but innerjoin can get the results in an instant. It turned out to be because exsits needed to match 400000 pieces of data from a dataset, which was very resource-intensive.

Summary:

First of all, to determine the data distribution, the efficiency of using exists is higher than that of innerjoin in the case of high hit, and the efficiency of using innerjoin is higher in the case of low hit rate.

If the data distribution is not clear, it is more stable to use innerjoin directly.

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