POSTGRESQL交叉表的实现

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POSTGRESQL交叉表的实现

来源: 作者: 时间:2016-01-27 10:35 【

这里我来演示下在POSTGRESQL里面如何实现交叉表的展示,至于什么是交叉表,我就不多说了,度娘去哦。
这里我来演示下在POSTGRESQL里面如何实现交叉表的展示,至于什么是交叉表,我就不多说了,度娘去哦。
t_girl=# select * from score; name | subject | score -------+---------+------- Lucy | English | 100 Lucy | Physics | 90 Lucy | Math | 85 Lily | English | 95 Lily | Physics | 81 Lily | Math | 84 David | English | 100 David | Physics | 86 David | Math | 89 Simon | English | 90 Simon | Physics | 76 Simon | Math | 79 (12 rows) Time: 2.066 ms
name | English | Physics | Math -------+---------+---------+------ Simon | 90 | 76 | 79 Lucy | 100 | 90 | 85 Lily | 95 | 81 | 84 David | 100 | 86 | 89
1、用标准SQL展现出来
t_girl=# select name, t_girl-# sum(case when subject = 'English' then score else 0 end) as "English", t_girl-# sum(case when subject = 'Physics' then score else 0 end) as "Physics", t_girl-# sum(case when subject = 'Math' then score else 0 end) as "Math" t_girl-# from score t_girl-# group by name order by name desc; name | English | Physics | Math -------+---------+---------+------ Simon | 90 | 76 | 79 Lucy | 100 | 90 | 85 Lily | 95 | 81 | 84 David | 100 | 86 | 89 (4 rows) Time: 1.123 ms
2、用PostgreSQL 提供的第三方扩展 tablefunc 带来的函数实现
t_girl=# SELECT * FROM crosstab('select name,subject,score from score order by name desc',$$values ('English'::text),('Physics'::text),('Math'::text)$$) AS score(name text, English int, Physics int, Math int); name | english | physics | math -------+---------+---------+------ Simon | 90 | 76 | 79 Lucy | 100 | 90 | 85 Lily | 95 | 81 | 84 David | 100 | 86 | 89 (4 rows) Time: 2.059 ms


t_girl=# select name,split_part(split_part(tmp,',',1),':',2) as "English", t_girl-# split_part(split_part(tmp,',',2),':',2) as "Physics", t_girl-# split_part(split_part(tmp,',',3),':',2) as "Math" t_girl-# from t_girl-# ( t_girl(# select name,string_agg(subject||':'||score,',') as tmp from score group by name order by name desc t_girl(# ) as T; name | English | Physics | Math -------+---------+---------+------ Simon | 90 | 76 | 79 Lucy | 100 | 90 | 85 Lily | 95 | 81 | 84 David | 100 | 86 | 89 (4 rows) Time: 2.396 ms


create or replace function func_ytt_crosstab_py () returns setof ytt_crosstab as $ytt$ for row in plpy.cursor("select name,string_agg(subject||':'||score,',') as tmp from score group by name order by name desc"): a = row['tmp'].split(',') yield (row['name'],a[0].split(':')[1],a[1].split(':')[1],a[2].split(':')[1]) $ytt$ language plpythonu; t_girl=# select name,english,physics,math from func_ytt_crosstab_py(); name | english | physics | math -------+---------+---------+------ Simon | 90 | 76 | 79 Lucy | 100 | 90 | 85 Lily | 95 | 81 | 84 David | 100 | 86 | 89 (4 rows) Time: 2.687 ms
5、 用PLPGSQL来实现

t_girl=# create type ytt_crosstab as (name text, English text, Physics text, Math text);
CREATE TYPE
Time: 22.518 ms


create or replace function func_ytt_crosstab ()
returns setof ytt_crosstab
as 
$ytt$
  declare v_name text := '';
                v_english text := '';
		v_physics text := '';
		v_math text := '';
		v_tmp_result text := '';
  declare cs1 cursor for select name,string_agg(subject||':'||score,',') from score group by name order by name desc;
begin
  open cs1;
  loop
    fetch cs1 into v_name,v_tmp_result;
    exit when not found;
    v_english = split_part(split_part(v_tmp_result,',',1),':',2);
    v_physics = split_part(split_part(v_tmp_result,',',2),':',2);
    v_math = split_part(split_part(v_tmp_result,',',3),':',2);
    return query select v_name,v_english,v_physics,v_math;
  end loop;
end;
$ytt$ language plpgsql;


t_girl=# select name,English,Physics,Math from func_ytt_crosstab();
 name  | english | physics | math 
-------+---------+---------+------
 Simon | 90      | 76      | 79
 Lucy  | 100     | 90      | 85
 Lily  | 95      | 81      | 84
 David | 100     | 86      | 89
(4 rows)


Time: 2.127 ms



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