北郵大三數(shù)據(jù)庫實驗六數(shù)據(jù)查詢分析實驗(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：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）對下面兩個查詢進行比較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
環(huán)評公示相關(guān)推薦
鄂ICP備17016276號-1