Question

我有查询：

SELECT ordernumber, orderdate, customername, orderline.isbn, title, orderline.numcopies, stock, shipmentbook.numcopies as shipcopies, authorname
                    FROM mousavs.author natural join mousavs.bookauthor natural join mousavs.book left join mousavs.bookorder 
                    natural join mousavs.orderline
                    ON book.isbn = orderline.isbn 
                    left join mousavs.shipmentbook
                    ON book.isbn = shipmentbook.isbn
                    WHERE stock > orderline.numcopies
                    ORDER BY  orderdate, ordernumber, ISBN

我得到了表格：

这里有多个字段是相同的，除了一本书有多个作者的authorname。我试图使用＆＃34; GROUP BY ordernumber＆＃34;每本书只显示一行。但是我得到一个错误：`＆＃34;错误代码：1055。SELECT列表的表达式＃4不在GROUP BY子句中，并且包含非聚合列＆m ;; mousavs.orderline.isbn＆＃39;它在功能上不依赖于GROUP BY子句中的列;

我的数据库结构：

预期结果：

ordernumber orderdate   customername    isbn    title   numcopies   stock   shipcopies  authorname
N201699998  2016-12-24  "Mary Hall" 1491936169  "Kafka: The Definitive Guide: Real-Time Data and Stream Processing at Scale"    2   14  1   "Neha Narkhede"
N201799999  2017-01-03  "Aran Clauson"  1491936169  "Kafka: The Definitive Guide: Real-Time Data and Stream Processing at Scale"    1   14  1   "Gwen Shapira"
N201700004  2017-03-01  "Chris Reedy"   0321399420  "Databases, Types and the Relational Model" 1   5   1   "Hugh Darwen"
N201700003  2017-05-01  "Filip Jagodzinski" 0321399420  "Databases, Types and the Relational Model" 1   5   1   "Hugh Darwen"
N201700006  2017-05-15  "Chris Reedy"   1118063333  "Operating System Concepts" 1   16  NULL    "Peter Galvin"
N201700006  2017-05-15  "Chris Reedy"   1449328016  "Database Design and Relational Theory: Normal Forms and All That Jazz (Theory in Practice)"    1   3   NULL    "C. J. Date"

更简单的查询：

SELECT book.isbn, title, ordernumber, orderdate, customername, numcopies, orderline.bookprice, authorname
                    FROM author natural join bookauthor natural join book left join orderline natural join bookorder
                    ON book.isbn = orderline.isbn
                    WHERE book.isbn = ?

Answer 1

查看提供的示例，您可以使用聚合函数（例如：authorname上的min）

SELECT 
    ordernumber
    , orderdate
    , customername
    , orderline.isbn
    , title
    , orderline.numcopies
    , stock
    , shipmentbook.numcopies as shipcopies
    , min(authorname)
FROM mousavs.author natural join mousavs.bookauthor natural join mousavs.book left join mousavs.bookorder 
natural join mousavs.orderlin ON book.isbn = orderline.isbn 
left join mousavs.shipmentbook  ON book.isbn = shipmentbook.isbn
WHERE stock > orderline.numcopies
GORUP BY ordernumber
    , orderdate
    , customername
    , orderline.isbn
    , title
    , orderline.numcopies
    , stock
    , shipmentbook.numcopies as shipcopies
ORDER BY  orderdate, ordernumber, ISBN

但你也可以使用group_concat（authorname）获得单行结果，其中所有的autor都在行中

  SELECT 
    ordernumber
    , orderdate
    , customername
    , orderline.isbn
    , title
    , orderline.numcopies
    , stock
    , shipmentbook.numcopies as shipcopies
    , group_concat(authorname)
FROM mousavs.author natural join mousavs.bookauthor natural join mousavs.book left join mousavs.bookorder 
natural join mousavs.orderlin ON book.isbn = orderline.isbn 
left join mousavs.shipmentbook  ON book.isbn = shipmentbook.isbn
WHERE stock > orderline.numcopies
GORUP BY ordernumber
    , orderdate
    , customername
    , orderline.isbn
    , title
    , orderline.numcopies
    , stock
    , shipmentbook.numcopies as shipcopies
ORDER BY  orderdate, ordernumber, ISBN

使用group by从mysql select查询中删除类似字段

1 个答案: