如何简化查询以检索 Oracle 中的详细信息？

Question

我需要在 Oracle 中编写一个查询来检索在销售、纺织和市场营销部门工作的员工的详细信息。但是当员工在市场部工作时，我只需要获得部门位置在美国和欧盟的员工。

销售和纺织品的位置列在部门 table 中为 NULL。

例如，

部门table:

dept_id   emp_id    dep_name       location 
D_1       A1130    MARKETING         US  
D_2       A1132    SALES             (null)
D_3       A1133    TEXTILES          (null)
D_4       A1134    MARKETING         US 
D_5       A1135    MARKETING         EU

我写了下面的查询。有没有其他替代方法可以简单地编写它而不是使用 UNION 并编写两次代码？

请帮帮我

SELECT emp.emp_id,
      emp.first_name ||' '|| emp.last_name employee_name,
      dept.department_name
FROM department dept,             
    employee emp,
    salary sal
WHERE emp.emp_id = dept.emp_id
 and dept.dept_id = sal.dept_id
 and emp.emp_id = 'A1130'
 and dept.department_name in ( 'SALES',
                             'TEXTILES')
UNION
SELECT emp.emp_id,
     emp.first_name ||' '|| emp.last_name employee_name,
     dept.department_name
FROM department dept,             
    employee emp,
    salary sal
WHERE emp.emp_id = dept.emp_id
 and dept.dept_id = sal.dept_id 
 and emp.emp_id = 'A1130'
 and dept.department_name in ( 'MARKETING')
 and dept.locations in ('US','EU');

Answer 1

retrieve the details of employees who work either in Sales, Textiles and Marketing. But when the employees work in Marketing, I need to get only those employees whose department location is US and EU.

您可以在没有 UNION 的情况下执行此操作，在 WHERE 子句中使用 ORed 条件：

SELECT 
    emp.emp_id,
    emp.first_name ||' '|| emp.last_name employee_name,
    dept.department_name
FROM 
    department dept
    INNER JOIN employee emp ON emp.emp_id = dept.emp_id
    INNER JOIN salary sal ON dept.dept_id = sal.dept_id
WHERE 
    emp.emp_id = 'A1130'
    AND (
        dept.department_name in ('SALES', 'TEXTILES')
        OR (dept.department_name = 'MARKETING' AND dept.locations in ('US','EU'))
    )

旁注：始终使用显式连接（使用 ON 关键字）而不是老式的隐式连接（使用 table 列表在 FROM 条款中），二十多年前就失宠了。

如何简化查询以检索 Oracle 中的详细信息？

How to simplify the query to retrieve the details in Oracle?

sql

oracle

union

duplicates

simplify