北郵大三數(shù)據(jù)庫實(shí)驗(yàn)六數(shù)據(jù)查詢分析實(shí)驗(yàn)(編輯修改稿)
2025-07-23 11:57 本頁面
【文章內(nèi)容簡介】 效率較高（2）select student_id,student_name,birthdayfrom student s1where birthday=(select max(birthday)from student s2where = ）另一個(gè)：select department,max(birthday) as maxAge into tmpfrom studentgroup by department。select student_id,student_name,birthdayfrom student,tmpwhere = and =drop table tmp查詢結(jié)果來看，重寫的執(zhí)行時(shí)間要快一些，但相差不多，如果數(shù)據(jù)庫比較大的話，執(zhí)行效果也許更明顯（3）對(duì)下面兩個(gè)查詢進(jìn)行比較select student_name,birthdayfrom studentwhere department!=39。電信39。 and birthday all(select birthdayfrom studentwhere department =39。電信39。）另：select student_name,birthdayfrom studentwhere department!=39。電信39。 and bir
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