relational-algebra - 将 SQL 转换为关系代数

Question

请任何人都可以帮助将以下两个 SQL 语句转换为关系代数

1)

SELECT D.Dname 
FROM Employee E, Department D
WHERE E.Dno = D.Dno
  AND E.Lname='Smith'
  AND S.Fname='John'

2)

SELECT B.Town
FROM Staff S, Branch B
WHERE S.BranchId = B.BranchId
  AND S.lName='Pincher'
  AND S.fName='Penny'

Answer 1

...我想你的意思是 D.Fname = 'John' 在 WHERE 子句

Answer 2

这是第二个 SQL 语句的关系代数：

π _Town (σ _{lName = 'Pincher' ^ fName = 'Penny'} (Staff |x| _BranchId Branch))

Answer 3

π _Dname (σ _{Lname = 'Smith' ^ Fname = 'John'} (Employee |x| _Dno Department))