这是我的表:
Table A which has entries with "item" and "grade" fields
Table B which has entries with A.id
Tuple table B-C
我想要所有具有 item= "x" 和 Grade = "y" 的 A 条目以及与 B 条目相关联的所有 C 条目,该条目与具有 item = "x" 和grade = "y" 的 A 条目相关联"
例如
A table:
A.item = "x", A.Grade = "y", A.id = 1
A.item = "x", A.Grade = "y", A.id = 2
A.item = "x", A.Grade = "y", A.id = 3
A.item = "r", A.Grade = "z", A.id = 4
B Table
B.AID = 1, B.id = 10
B.AID = 1, B.id = 11
B.AID = 2, B.id = 13
B.AID = 3, B.id = 14
B.AID = 4, B.id = 15
B-C Tuple Table
BID = 10, CID = 20
BID = 11, CID = 20
BID = 13, CID = 20
BID = 15, CID = 21
该查询应返回 A 表中的所有条目以及 C 表中的条目 20 但不返回 21,因为 C.id = 21 仅与与不满足项目和等级要求的 A 关联的 B 进行元组。