但是一些聚合函数比如array_agg或者string_agg产生的结果就依赖于输入行的顺序,这就需要order_by_clause来指定需要的顺序: Distinct若加order by,则order by列只能是distinct列,distinct本身在进行计算的时候就会重新对distinct列进行排序,可以这么说,加上order by也是多余的: 对于普通聚合和统计
在这个场景中,我们可以使用string_agg函数来合并每个客户的所有产品名称。string_agg函数接受两个参数:第一个参数是要聚合的列,第二个参数是分隔符。 3. 根据实际需求进行排序或去重操作 在合并之前,我们可能希望对product_name进行排序或去重。这可以通过在string_agg函数中使用ORDER BY子句和DISTINCT关键字来实现。
-- 7、pgsql合并函数string_agg SELECT ltrim(rtrim(name)),string_agg(distinct(grade), '#') "grade" from student GROUP BY ltrim(rtrim(name)) -- 8、pgsql转数组 SELECT ltrim(rtrim(name)),"array_agg"(distinct(grade)) "grade" from student GROUP BY ltrim(rtrim(name)) -- 9、取最新的一...
string_agg(ccc,' \r\n ') 3.如果要将多个字段的值拼接成一个: string_agg(concat_ws(':',aaa,bbb),' \r\n ' order by aaa asc) as xxx 1. 2. 3. 4. 5. 6. 7. 查询所有字段 排除某些字段 SELECT 'SELECT ' || array_to_string(ARRAY(SELECT 'o' || '.' || c.column_name FROM...
select nameid, string_agg(traffic,',') from dbscheme.test0001 group by nameid order by nameid ; 去重 select nameid, string_agg(distinct traffic,',') from dbscheme.test0001 group by nameid order by nameid ; 排序 select nameid, string_agg(traffic,',' order by traffic) from dbscheme...
string_agg( 'Pid: '||case when pid is null then 'NULL' else pid::text end||chr(10)|| 'Lock_Granted: '||case when granted is null then 'NULL' else granted::text end||' , Mode: '||case when mode is null then 'NULL' else mode::text end||' , FastPath: '||case when fas...
1349d27 added code to adjust the PlannerInfo.group_pathkeys so that ORDER BY / DISTINCT aggregate functions could obtain pre-sorted inputs to allow faster execution. That commit forgot to adjust the pathkeys in create_agg_path(). Some code in there assumed that it was always fine to make...
[ GROUP BY grouping_element [, ...] ] [ HAVING condition [, ...] ] [ WINDOW window_name AS ( window_definition ) [, ...] ] [ { UNION | INTERSECT | EXCEPT } [ ALL | DISTINCT ] select ] [ ORDER BY expression [ ASC | DESC | USING operator ] [ NULLS { FIRST | LAST } ...
postgresql 查找PL/PGSQL函数以返回N列如果不在某个地方对列列表进行硬编码（无论是在调用函数时还是在...
PostgreSql中则是string_agg()函数 2、语法结构 2.1 MySql 默认的分隔符是逗号"," group_concat([distinct]要连接的字段[orderby排序字段asc|desc][separator'分隔符']) 1. 2.2 PostgreSql 必须指定分隔符 string_agg(要连接的字段,'分隔符'[orderby排序字段{asc|desc},[...]]) ...