SQL Oracle缺少關鍵字

Question

create table EmployeesUK_9035
  2  as
  3  select e.employee_id,e.first_name || e.Last_name "Name",e.Salary,l.City,e.hire_date from employees e join locations l
  4  where e.employee_id in(select e.employee_id from employees e join departments d on(e.department_id=d.department_id) join locations l on(d.location_id=l.location_id) where l.city='London');

Answer 1

... from employees e join locations l
4 where from employees e join locations l
4 where

您已經錯過了JOIN子句的ON部分（在主查詢中，而不是子查詢中）。

這是那種燈籠褲，應該很容易發現。 但是，由於您的代碼堆積如山，因此很難診斷。 很好地布置代碼不只是經驗豐富的開發人員精打細算：可讀性實際上是代碼的功能。 像這樣 ...

create table EmployeesUK_9035
as
select e.employee_id,
    e.first_name || e.Last_name "Name",
    e.Salary,
    l.City,
    e.hire_date 
from employees e 
     join locations l

where e.employee_id in (select e.employee_id 
                        from employees e 
                             join departments d 
                                 on (e.department_id=d.department_id) 
                             join locations l 
                                 on (d.location_id=l.location_id) 
                        where l.city = 'London')
    ;

看到發現缺失線有多容易？ 您需要一個ON子句才能連接EMPLOYEES和LOCATIONS。 但是，考慮到子查詢的聯接，您可能還需要在主查詢中包括DEPARTMENTS，因為兩個表之間似乎沒有聯接。 在這種情況下，查詢可能會簡化為

create table EmployeesUK_9035
as
select e.employee_id,
    e.first_name || e.Last_name "Name",
    e.Salary,
    l.City,
    e.hire_date 
from employees e 
     join departments d 
        on (e.department_id=d.department_id) 
    join locations l 
        on (d.location_id=l.location_id) 
where l.city = 'London'
;

---

順便說一句，在創建表時，請不要對列別名使用雙引號和大小寫混合大小寫。 每次引用時，您都必須在雙引號中使用"Name" ，並且使用完全相同的大小寫，這很麻煩，因為Oracle代碼通常不區分大小寫。 也就是說，默認情況下，所有Oracle標識符都是大寫的，但是大小寫無關緊要，只要我們不將標識符用雙引號引起來即可。

Answer 2

JOIN應該打開（以顯示您要連接的表的內容），而您的沒有。

我將ON 1 = 1設置為ON 1 = 1 ，但您應該使用EMPLOYEES和LOCATIONS表中的列。

CREATE TABLE EmployeesUK_9035
AS
   SELECT e.employee_id,
          e.first_name || e.Last_name "Name",
          e.Salary,
          l.City,
          e.hire_date
     FROM employees e JOIN locations l 
                      ON 1 = 1                      --> this
    WHERE e.employee_id IN (SELECT e.employee_id
                              FROM employees e
                                   JOIN departments d
                                      ON (e.department_id = d.department_id)
                                   JOIN locations l
                                      ON (d.location_id = l.location_id)
                             WHERE l.city = 'London');