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

(benefits of precompilation: 1. The execution plan can be reused to reduce the time required for sql compilation. two。 It is used many times at a time. 3. Avoid sql injection. )

(implicit conversion occurs when columns and parameter types are inconsistent)

Not in may cause index failure

For example, sql injects one database, but cannot see another database

(the results of the subquery are saved in the temporary table, and the index cannot be used in either the memory temporary table or the disk temporary table.)

Indexes are rarely used in or.

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