FIRST_VALUE、LAST_VALUE分析函數可以按照特定分組和排序取出組內首尾值，語法

FIRST_VALUE { (expr) [ {RESPECT | IGNORE} NULLS ]| (expr [ {RESPECT | IGNORE} NULLS ])}OVER (analytic_clause)

測試下

10:48:07 SCOTT@study> SELECT EMPNO, 10:48:15 2 DEPTNO, 10:48:15 3 SAL, 10:48:15 4 FIRST_VALUE(SAL) IGNORE NULLS OVER(PARTITION BY DEPTNO ORDER BY SAL) AS LOWEST_IN_DEPT, 10:48:15 5 FIRST_VALUE(SAL) IGNORE NULLS OVER(PARTITION BY DEPTNO ORDER BY SAL ROWS 1 PRECEDING) AS PRECEDING_IN_DEPT, 10:48:15 6 LAST_VALUE(SAL) IGNORE NULLS OVER(PARTITION BY DEPTNO ORDER BY SAL) AS HIGHEST_IN_DEPT, 10:48:15 7 LAST_VALUE(SAL) IGNORE NULLS OVER(PARTITION BY DEPTNO ORDER BY SAL ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS HIGHEST_IN_DEPT 10:48:15 8 FROM EMP;EMPNO DEPTNO SAL LOWEST_IN_DEPT PRECEDING_IN_DEPT HIGHEST_IN_DEPT HIGHEST_IN_DEPT ---------- ---------- ---------- -------------- ----------------- --------------- ---------------7934 10 1300 1300 1300 1300 50007782 10 2450 1300 1300 2450 50007839 10 5000 1300 2450 5000 50007369 20 800 800 800 800 30007876 20 1100 800 800 1100 30007566 20 2975 800 1100 2975 30007788 20 3000 800 2975 3000 30007902 20 3000 800 3000 3000 30007900 30 950 950 950 950 28507654 30 1250 950 950 1250 28507521 30 1250 950 1250 1250 28507844 30 1500 950 1250 1500 28507499 30 1600 950 1500 1600 28507698 30 2850 950 1600 2850 285014 rows selected.Elapsed: 00:00:00.00 10:48:17 SCOTT@study>

LAST_VALUE的默認寫法結果不符合預期，是因為默認的開窗語句"RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW"，所以需要顯性寫出正確的開窗語句

轉載于:https://www.cnblogs.com/yongestcat/p/11248907.html

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