数据库in/exists用法和效率大揭密

以前没注意到这二者的差异。java 其实，这里仍是有必定的陷阱的。oop 先看下代码：spa select count(*) from ( ( select sc.xh from "JISUANJI"."STUDENTCHECK" sc ) union ( select stu.XH as xh from "JISUANJI"."CVARIABLE" cv , "

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