将 SQL 转换为关系代数
请任何人帮忙将以下两个 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'
Please can anyone help convert the following two SQL statements to Relational Algebra
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'
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评论（3）
...我想你的意思是 WHERE 子句中的 D.Fname = 'John'
... and I suppose you meant D.Fname = 'John' in WHERE clause
下面是第二条 SQL 语句的关系代数：
π Town (σ lName = 'Pincher' ^ fName = 'Penny' (Staff |x| BranchId分支））
Here's the relational algebra for the second SQL statement:
π Town (σ lName = 'Pincher' ^ fName = 'Penny' (Staff |x| BranchId Branch))
π Dname (σ Lname = 'Smith' ^ Fname = 'John' (员工 |x| Dno 部门))
π Dname (σ Lname = 'Smith' ^ Fname = 'John' (Employee |x| Dno Department))