sql - 如何重构这个 SQL 查询？

Question

我正在向 IBM DB2 服务器写入以下查询:

SELECT 
    EMPNO, 
    YEAR(CURRENT TIMESTAMP - BIRTHDATE) AS AGE,
    DENSE_RANK() OVER(ORDER BY YEAR(CURRENT TIMESTAMP - BIRTHDATE) ASC) AS RANK

FROM 
    DANDY.EMPLOYEE;

它有效，但看起来很丑，因为我正在重复表达式:

YEAR(CURRENT TIMESTAMP - BIRTHDATE)

但是这样写是行不通的:

DENSE_RANK() OVER(ORDER BY AGE ASC) AS RANK

如何让它变得更好？

Answer 1

SELECT 
EMPNO, 
AGE,
DENSE_RANK() OVER(ORDER BY AGE ASC) AS RANK
FROM (SELECT EMPNO,
             YEAR(CURRENT TIMESTAMP - BIRTHDATE) AS AGE
      FROM DANDY.EMPLOYEE);