CTGU-2023春-MySQL数据库实验3_3-查询789

第一关

 use library;######### Begin ###########  -- 7、查询所有曾经借过书号为“A04500049”这本书的所有用户的借阅证号和姓名
select loanNo,lname
from Users
where loanNo =some (select loanNo from LoanHist where bookNo='A04500049' );######### End ##########

第二关（运行第二关代码时，先跑一遍第一关代码）

 use library;######### Begin ########## -- 8、查询所有借过书的用户借阅证号select distinct loanNofrom Userswhere loanNo =some(select loanNo from Loan)unionselect distinct loanNofrom Userswhere loanNo =some(select loanNo from LoanHist);######### End ##########

第三关

 use library;######### Begin #########
##    -- 9、查询现在正借有书的用户但以前没有借过书的用户的借阅证号select distinct loanNo from Loanwhere loanNo <>all (select loanNo from LoanHist);######### End ##########

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