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postgresql行转列

时间:2018-08-26 01:13:55      阅读:776      评论:0      收藏:0      [点我收藏+]

标签:cross   cte   插入   integer   oss   data   random   交叉表   不重复   

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问:怎么分页&&按条件&&按顺序&&姓名不重复查出数据?

答:其实就是行转列,那么,postgresql怎么进行转列呢,百度了下,大概有三种写法

 

写法1 

group by + sum + case when

select name,
sum(case when zbfm=年龄 then value else 0 end) as 年龄,
sum(case when zbfm=身高 then value else 0 end) as 身高,
sum(case when zbfm=体重 then value else 0 end) as 体重
from test group by name
having name like %1 and length(name)=4 order by 年龄 desc

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写法2

用postgresql的crosstab交叉函数

crosstab(unknown, unknown) does not exist

select * from
crosstab(
select name,zbfm,value from test where name like ‘‘%1‘‘ and length(name)=4,$$values(年龄), (身高), (体重)$$) as score(name text, 年龄 int, 身高 int, 体重 int) order by 年龄 desc

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写法3

group by + string_agg + split_part(分组,行转列,字符切割)

select name, 
split_part(split_part(temp,,,1),:,2) as 年龄,
split_part(split_part(temp,,,2),:,2) as 身高,
split_part(split_part(temp,,,3),:,2) as 体重
from(
select name, string_agg(zbfm||:||value,,) as temp from test
group by name 
having name like %1 and length(name)=4
) as t order by 年龄 desc

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group by + string_agg

select name, string_agg(zbfm||:||value,,) from test
group by name 
having name like %1 and length(name)=4

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其他

建表语句

CREATE TABLE test
(
  id serial NOT NULL,
  value integer,
  name character varying,
  zbfm character varying,
  CONSTRAINT pkey PRIMARY KEY (id)
)

插入数据(python)

import psycopg2
from random import random
conn = psycopg2.connect(database="postgres", user="postgres", password="password", host="ip", port="port")
cur = conn.cursor()

def insertData():
    names = [路人甲, 王尼玛, 唐马儒]
    zbfms = [年龄, 身高, 体重]

    for i in range(100):
        sqlstr = insert into test(name, zbfm, value) values
        for j in range(100):
            for name in names:
                for zbfm in zbfms:
                    sqlstr += "(‘%s‘,‘%s‘,%d),"%(name+str(i*100+j),zbfm,int(100*random()))
        cur.execute(sqlstr[:-1])
        conn.commit()
        print(i)

if __name__ == __main__:
    insertData()
    selectData()

 

 

参考

PostgreSQL 实现交叉表(行列转换)的五种方法

postgresql行转列

标签:cross   cte   插入   integer   oss   data   random   交叉表   不重复   

原文地址:https://www.cnblogs.com/lurenjia1994/p/9535899.html

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