SELECTcount(DISTINCTfee_date)asdisfromnew_orderwherenews_id='novel'andorder_status='2' 二、sql执行顺序 from语句->where语句->group by语句->having语句->order by语句->select 语句 三、row_number()分析函数 说明:返回结果集分区内行的序列号,每个分区的第一行从 1 开始。 语法:ROW_NUMBER () OVER ...
SELECT array_distinct(hobbies::integer[]) AS distinct_hobbies FROM users; 结合ROW_NUMBER 和窗口函数: 虽然这种方法相对复杂一些,但在某些情况下可能更灵活。它利用窗口函数为数组中的每个元素分配一个唯一的行号,然后通过这个行号来去重。 sql WITH unnested AS ( SELECT UNNEST(hobbies) AS hobby, ROW_NUMB...
SELECT count(DISTINCT fee_date) as dis from new_order where news_id='novel' and order_status='2'这两个SQL执⾏所得到的数据是⼀样的!⼯具:postgreSQL 1.我们要清楚,sql的执⾏顺序:from语句->where语句->group by语句->having语句->order by语句->select 语句 2.row_number()分析函数 说...
除了ROW_NUMBER() 之外,RANK() 或者 DENSE_RANK() 函数也可以实现以上功能。关于窗口函数的介绍和使用案例,可以参考这篇文章。 我们可以基于该查询结果删除重复的记录: DELETE FROM people WHERE id IN ( SELECT id FROM ( SELECT id, name, email, row_number() over (PARTITION BY email ORDER BY id DESC...
# select * from (select row_number() over (partition by a) as rn, * from t_distinct) t where rn=1; rn | a | b | c ---+---+---+--- 1 | 1 | 2 | 3 1 | 2 | 2 | 3 1 | 3 | 3 | 4 1 | 4 | 4 | 5 1 | 5 | 6 | 1 | 6 | 7 | (6 rows) 1...
其中,第一个语句使用了子查询;第二个语句使用了窗口函数,除了 ROW_NUMBER 之外,也可以使用 RANK 或者 DENSE_RANK 等函数。这两者都是 SQL 标准实现。除此之外,PostgreSQL 提供了扩展的 DISTINCT ON 子句,可以更加方便地实现以上结果:SELECT DISTINCT ON (dept_id) dept_id, emp_name, salary ORDER BY ...
PostgreSQL ROW_NUMBER() function and DISTINCT operator The following query uses the ROW_NUMBER() function to assign integers to the distinct prices from the products table. SELECT DISTINCT price, ROW_NUMBER () OVER ( ORDER BY price ) FROM products ORDER BY price; However, the result is not...
此外,有一点需要大家特别注意,即:关键字 distinct 只能放在 SQL 语句中所有字段的最前面才能起作用,如果放错位置,SQL 不会报错,但也不会起到任何效果。 2、row_number() over() 在oracle数据库中,为咱们提供了一个函数 row_number() 用于给数据库表中的记录进行标号,在使用的时候,其后还跟着一个函数 over(...
select distinct tsg.member_code memberCode,row_number() OVER (order by consumer_date ) AS rownum,tsg.SCORE_TYPE ,<!-- tsd.CONSUMEORG businessOrg, --> <!-- tsd.GRANTORG grantOrg, -->tsd.GRENT_PROJECT, to_char(tsd.insert_time,'yyyy-MM-dd') insertTime, ...
postgres=# select count(distinct c3) from tbl; count --- 11 (1 row) postgres=# select count(distinct (c3,c2)) from tbl; count --- 1111 (1 row) postgres=# explain (analyze,verbose,timing,costs,buffers) select count(distinct (c3,c2)) from tbl;; QUERY PLAN --- Aggregate (cost=179...