SQL - 逐年查询

Question

I have a table of employees' info, including their employment start and end date. I want to extract a list of employees who have been with the company for the full year, year by year, for the past ten years.

So for example, if I want to get a list of employees who've been with the company throughout 2010, I'll do a query like this:

SELECT employee_name FROM employees
WHERE employment_start_date < DATE '2010-01-01'
AND employment_end_date > DATE '2010-12-31'

Now, I could repeat this process manually 10 times for each year from 2010 to 2020 (and manually append the relevant year as an additional column), but surely there's an easier way to do this with a single SQL query?

More background info: I'm actually trying to translate my Cypher query directly into an SQL query (because different companies uses different database system). Using Cypher, I'll be doing this:

WITH [2010,2011,2012,...,2019,2020] AS years
UNWIND years as y
MATCH (e:employees)
WHERE e.employment_start_date.year < y
AND e.employment_end_date.year > y
RETURN y, e.employee_name

So I'm trying to find an SQL equivalent for this

---

Sample table data:

|employee_name|employment_start_date|employment_end_date|
|:---:|:---:|:---:|
|John|2009-06-01|2015-03-02|
|Mary|2010-04-02|2014-03-07|
|Joseph|2011-03-02|2011-07-03|
|Stephen|2003-06-14|2011-03-07|
|Dew|2010-06-02|2012-02-06|

Desired Results:

|Year|employee_name|
|:---:|:---:|
|2010|John|
|2010|Stephen|
|2011|John|
|2011|Mary|
|2011|Dew|

Answer 1

You can use:

WITH years ( year ) AS (
  SELECT DATE '2010-01-01' FROM DUAL
UNION ALL
  SELECT ADD_MONTHS( year, 12 )
  FROM   years
  WHERE  year < DATE '2020-01-01'
)
SELECT y.year, e.employee_name
FROM   employees e
       INNER JOIN years y
       ON (   e.employment_start_date <= y.year
          AND e.employment_end_date   >=  ADD_MONTHS( y.year, 12 ) )

Answer 2

An alternative to MT0's suggestion:

WITH years (year) AS(
SELECT EXTRACT (YEAR FROM DATE '2010-01-01') + ROWNUM -1 AS "YEAR"
FROM dual
CONNECT BY ROWNUM <=10
)

SELECT y.year, e.employee_name
FROM employee e
INNER JOIN years y
ON (
EXTRACT(YEAR FROM employment_start_date) < y.year
AND EXTRACT(YEAR FROM employment_end_date) > y.year
)