MySQL表查找查詢

我很難實現這些查詢。有人可以幫忙嗎？MySQL表查找查詢

查詢1：查找在同一分店至少參加過兩次考試的駕駛員姓名。

查詢2：查找當他/她參加更多考試時考試分數變低的駕駛員的姓名。

我的代碼

create table branch(branch_id integer, branch_name varchar(20), branch_addr varchar(50), branch_city varchar(20), branch_phone integer); 
create table driver(driver_ssn integer, driver_name varchar(20), driver_addr varchar(50), driver_city varchar(20), driver_birthdate date, driver_phone integer); 
create table license(license_no integer, driver_ssn integer, license_type char, license_class integer, license_expiry date, issue_date date, branch_id integer); 
create table exam(driver_ssn integer, branch_id integer, exam_date date, exam_type char, exam_score integer); 

insert into branch values(10,'Main','1234 Main St.','Vancouver',5551234); 
insert into branch values(20,'Richmond','23 No. 3 road','Richmond',5552331); 
insert into branch values(30,'West Creek','251 creek rd.','Sechelt',5552511); 
insert into branch values(40,'Blenheim','1342 W.22 Ave.','Burnaby',5551342); 

insert into driver values(11111111, 'Bob Smith','111 E.11 st.', 'Vancouver', '1975-01-01',5551111); 
insert into driver values(22222222, 'John Walters','222 E.22 st.', 'Burnaby', '1976-02-02',5552222); 
insert into driver values(33333333, 'Troy Rops','333 W.33 ave.', 'Richmond', '1970-03-03',5553333); 
insert into driver values(44444444, 'Kevin Mark','444 E.4 ave.', 'Vancouver', '1974-04-04',5554444); 

insert into license values(1, 11111111,'D', 5, '1999-05-25','1997-05-25',20); 
insert into license values(2, 22222222,'D', 5, '1998-08-29','1996-08-29',40); 
insert into license values(3, 33333333,'L', 5, '1997-12-27','1997-06-27',20); 
insert into license values(4, 44444444,'D', 5, '1999-08-30','1997-08-30',40); 

insert into exam values(11111111,20, '1997-05-25', 'D',79); 
insert into exam values(11111111,20, '1997-12-02', 'L',97); 
insert into exam values(22222222,30, '1996-05-06', 'L',25); 
insert into exam values(22222222,40, '1996-06-10', 'L',51); 
insert into exam values(22222222,40, '1996-08-29', 'D',81); 
insert into exam values(33333333,10, '1997-07-07', 'L',45); 
insert into exam values(33333333,20, '1997-06-27', 'L',49); 
insert into exam values(33333333,20, '1997-07-27', 'L',61); 
insert into exam values(44444444,10, '1997-07-27', 'L',71); 
insert into exam values(44444444,20, '1997-08-30', 'D',65);

我上查詢1嘗試：

select driver.driver_name 
from exam, branch, driver 
where driver.driver_ssn = exam.driver_ssn AND 
    (select exam.driver_ssn 
    from exam 
    group by exam.driver.ssn, exam.branch_id 
    having count(exam.branch_id) >= 2);

來源

2013-11-14 user1681664

家庭作業？也這麼覺得。他們在教JOIN之前教過子查詢嗎？這很糟糕。 – Strawberry

@Strawberry他們教過的連接，但不好。我試圖自己弄清楚 – user1681664

好了，第一查詢可能是這個樣子......

SELECT something 
    FROM somehere d 
    JOIN somewhere_else e 
    ON e.some_other_thing = d.some_other_thing 
GROUP 
    BY d.some_other_thing 
    , e.and_yet_another_thing 
HAVING COUNT(*) >= 2;

假設問題2種手段'找到後續考試分數低於前一分的司機的名字'，那麼這可能看起來像這樣......

SELECT DISTINCT d.driver_name 
      FROM ... d 
      JOIN ... preceding 
      ON preceding.... = d.... 
      JOIN ... subsequent 
      ON subsequent.... = preceding.... 
      AND subsequent.... > preceding.... 
      AND subsequent.... < preceding....;

來源

2013-11-15 10:59:00 Strawberry

first query something like this

select d.driver_name from driver d inner join exam e on d.driver_ssn=e.driver_ssn inner join branch b on e.branch_id=b.branch_id 

group by d.driver_name 
having count(*)>=2

來源

2013-11-15 11:50:30

MySQL表查找查詢

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