sql 涉及 3 个表的查询

Question

我有 3 个表：-

    Table_1               Table_2                    Table_3
------------------------  --------------------  --------------------
id  bk_title  strm_id     bk_no   bk_isbn            s_id    strm_name
-----------------------  ---------------------  -----------------------
1   A_Book    3           1       ISBN0001           3       Science
2   B_Book    4           1       ISBN0002           4       History
                          2       ISBN0003

我想获取记录为

BK_Title    Num_Copies  Stream
---------------------------------------
A_Book      2       Science
B_Book      1       History

我该怎么做so.Please建议。

Answer 1

试试这个：

SELECT BK_Title, COUNT(Table_2.bk_isbn) AS Num_Copies, Table_2.strm_name AS Stream
FROM Table_1
JOIN Table_2 on (Table_1.id = Table_2.bk_no)
JOIN Table_3 on (Table_1.strm_id = s_id)
GROUP BY BK_Title, strm_name
ORDER BY BK_Title

sql 涉及 3 个表的查询

sql query involving 3 tables

sql

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