Question

我有一个包含三个具有以下结构的表的方案

donuts (name: string, price: integer) 
grocery (no: string, gname: string, minCredit: integer) 
distributor (dname: string, gno: string, deliverydate: date)

distributor.dname和distributor.gno是引用甜甜圈和杂货的外键，哪些键是名称而且没有相应的我在遇到2个查询时遇到问题我想写：

查询名为“Jelly”的杂货店甜甜圈中具有最高minCredit要求的杂货（杂货店，编号：字符串）的数量
```
     SELECT g.no 
     FROM grocery g, distributor dd, donut d
     WHERE minCredit >= * AND d.name = "JELLY" 
```

这不起作用

查询每个甜甜圈共享的杂货编号（杂货店，编号：字符串）以及价格高于2的查询

我试过
```
SELECT g.no
FROM grocery g, distributor dd, donut d
WHERE g.price >= 2
```

这也不是正确的事情。任何帮助表示赞赏

Answer 1

尝试：

1

SELECT g.no
FROM grocery g, distributor dd, donut d
WHERE g.no = dd.gno
  AND d.name = dd.dname
  AND d.name = 'JELLY'
ORDER BY g.minCredit DESC LIMIT 1

2

SELECT g.no
FROM grocery g, distributor dd, donut d
WHERE g.no = dd.gno
  AND d.name = dd.dname
  AND d.price >= 2

从具有多个表的模式查询

1 个答案: