ORA 00918-列明确定义的错误 [英] ORA 00918- Column ambiguosly defined error

问题描述

我的Oracle数据库中有两个表.

There are two tables in my Oracle database.

第一个表是(客户)-

customer_id Customer_name Customer_age Customer_address salary
103 Giriraj Rathi      22   Kolkata    12000
100 Subir Adhikari     22   Bolpur     10000
101 Rakesh Chatterjee  21   Tarkeshwar 8000
102 Jayanta Patra      20   Tarkeshwar 9000
104 Abhi Karmakar      22   Burdwan    8000
105 Mainak Manna       21   Burdwan    9000
106 Subho Gupta        20   Kolkata    10000
107 Aritra Das         23   Kolkata    7000
108 Pradip Paul        22   Kolkata    5000
109 Sourav Banerjee    22   Bolpur     9000

第二张表是(订单"):

Second table is (Orders):

Order_id Order_date   customer_id  amount

200 12-03-13    100 1100
201 09-05-13    101 1400
202 07-04-12    103 2500
204 29-05-13    104 2400
203 09-02-13    105 9000
205 18-06-13    106 2100
206 09-07-13    107 1600
207 18-05-13    108 2900
209 18-04-13    109 2400

现在，我想同时加入这两个表.所以我使用了查询:

Now I wanted to join both the tables. So I used the query:

select customer_id,
       customer_name,
       customer_address, 
       order_id,order_date, 
       amount 
  from customers, 
       orders 
 where customers.customer_id=orders.customer_id; 

我搜索了该错误，并发现当SQL代码本身存在歧义时会发生这种情况，但是在这种情况下，我什么也看不到.

I Googled about the error and found this happens when there is ambiguity in the SQL code itself, but in this case I see nothing.

推荐答案

将表名/别名添加到这样的列总是一个好主意

It is always a good idea to add the table name/alias to the column like this

select c.customer_id,
       c.customer_name, 
       c.customer_address, 
       o.order_id,
       o.order_date,
       o.amount 
from customers c
inner join orders o on c.customer_id = o.customer_id

如果不这样做，那么数据库将不知道要采用哪一列，并且两个表都有一个名为customer_id的列.

If you don't then the DB don't know which column to take and both tables have a column named customer_id.

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