select (select count(*) from "News") as count, * from "News";
如果记录集有1000000个,这条SQL是执行10000001次查询,还是2次查询?
是否没得到一条记录集都要执行一次select count(*) from "News")??
效率如何?
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在线等待:关于嵌套查询次数问题
select (select count(*) from "News") as count, * from "News"; 如果记录集有1000000个,这条SQL是执行10000001次查询,还是2次查询? 是否没得到一条记录集都要执行一次select count(*) from "News")?? 效率如何?