Question

写一个在列中找到第三大整数的聚合？这就是我在做什么：

create function third_step(bigint, integer) returns bigint AS
$$

SELECT distinct
 * from count_lab order by ab asc limit 1 offset 2 ;


$$ language sql; --can we use plpgsql somehow?

create aggregate third_agg(integer)
(stype=bigint,sfunc=third_step,initcond=0); 
SELECT distinct
 * from count_lab order by ab asc limit 1 offset 2  ;

Answer 1

创建函数third_step（整数，ab整数）返回整数AS $$

选择与众不同 *从count_lab顺序开始，按ab asc限制1偏移2；

$$语言sql; -我们可以以某种方式使用plpgsql吗？

创建聚合的third_agg（integer）（stype = integer，sfunc = third_step，initcond = 0）; 选择不同 *从count_lab顺序开始，按ab asc限制1偏移2；

Answer 2

应该是：

SELECT DISTINCT ab 
    FROM count_lab 
    WHERE ab IS NOT NULL 
    ORDER BY ab DESC 
    LIMIT 1 OFFSET 2;

PostgreSQL找到第n个数字

2 个答案: