Quizzes 1

1. 一对多，哪个是FK？ The personid in CAR is the foreign key .
2. 如果这个attribute只在一个表里出现，就不需要item.color了

3. GROUP BY select max(sum(saleqty)) from qsale group by itemname (wrong) Nesting functions for ‘group by’ data is not allowed

   select count(* ) from qdel group by count(* ) order by splno desc;(wrong) ‘Group by count(* )’ gives a syntax error, because the group by clause needs to target un-grouped attributes (and group them). If the argument of group by was changed to ‘splno’, the query would be correct.

4. ‘FROM’ should be followed by the name of a table or query, not of a column
5. 
6. 
7. After ‘or’ there should be an expression, e.g. ‘or itemcolor = ‘white’. Instead, there is only a text string.

Quizzes 2

1. well-formed: tell the reader about the role of attributes
2. Waston don’t show the FK, 但是还是有点别的要求。
3. Table Book copy has two primary keys.(wrong) 每个表只能有一个PK，但是这个PK可以有很多个attribute
4. the FKs to the mother tables also need to be part of the PK 就是loan表里的tile, copy和borrower是引自别的表的，LOAN的外键，但是同时也是LOAN主键的一部分

   Quizzes 3

5. 一个员工可以是很多个部门的头，但是一个部门只能有一个头，员工是多端
6. 就是不join还是不行
7. <>就是不等于
8. ORDER BY 和GROUP BY Give sales in descending order of saleqty. select * from qsale
   order by saleqty desc;
9. COUNT() 和SUM（） Give the ==total number of deliveries== per item Count()只是计数行数， SUM()才是计算里面的 select itemname, sum(delqty) from qdel
   group by itemname
10. group by - having
11. 就是是Head还是boss的问题
12. either or both black and white
    1. where itemcolor in (‘Black’, ‘White’)
    2. where itemcolor = ‘Black’ or itemcolor = ‘White’
    3. select itemname from qitem
       where itemcolor = “Black” union select itemname from qitem
       where itemcolor = “White”;