本文将为您介绍如何对数据进行分组，取出每组数据的前N条数据。
示例数据
empno | ename | job | sal |
empno | ename | job | sal |
7369 | SMITH | CLERK | 800.0 |
7876 | SMITH | CLERK | 1100.0 |
7900 | JAMES | CLERK | 950.0 |
7934 | MILLER | CLERK | 1300.0 |
7499 | ALLEN | SALESMAN | 1600.0 |
7654 | MARTIN | SALESMAN | 1250.0 |
7844 | TURNER | SALESMAN | 1500.0 |
7521 | WARD | SALESMAN | 1250.0 |
实现方法
取出每条数据的行号，再用WHERE语句进行过滤。
SELECT * FROM (
SELECT empno
, ename
, sal
, job
, ROW_NUMBER() OVER (PARTITION BY job ORDER BY sal) AS rn
FROM emp
) tmp
WHERE rn < 10;