将未知行值动态转置为 postgres 上的列名
Dynamic transpose for unknown row value into column name on postgres
我有table这样的：
customer_number
label
value
1
address
St. John 1A
1
phone
111111111
1
email
john@cena.com
2
address
St. Marry 231A
2
phone
222222222
2
email
please@marry.me
我想要新的 table 或视图，所以它变成了：
customer_number
address
phone
email
1
St. John 1A
111111111
john@cena.com
2
St. Marry 231A
222222222
please@marry.me
但将来可能会添加不同的标签，例如可能会有名为 occupation 的新标签。
重要提示，我不知道标签列的值，所以它应该迭代到该列内的任何值。
有什么办法吗？
我使用交叉应用来解决这个问题..
这是我的查询
select distinct tb9.customer_number, tb9_2.*
from Table_9 tb9 cross apply
(select max(case when tb9_2.[label] like '%address%' then [value] end) as [address],
max(case when tb9_2.[label] like '%phone%' then [value] end) as [phone],
max(case when tb9_2.[label] like '%email%' then [value] end) as [email]
from Table_9 tb9_2
where tb9.customer_number = tb9_2.customer_number
) tb9_2;
一般来说SQL不擅长动态旋转
这是一个将为您转换数据的查询。但是，它不是动态的，即如果添加了未来的 occupation 标签，那么您将不得不更改查询。不确定是否可以接受：
select customer_number,
max(value) filter (where label='address') as address,
max(value) filter (where label='phone') as phone,
max(value) filter (where label='email') as email
from your_customer_table
group by customer_number
假设您是 运行 Postgres 9.4 或更高版本，以便支持 filter 功能。如果不是，则可以使用 case 语句重新处理它：
select customer_number,
max(case when label='address' then value else null end) as address,
max(case when label='phone' then value else null end) as phone,
max(case when label='email' then value else null end) as email
from your_customer_table
group by customer_number
您不能拥有“动态”数据透视表，因为查询的所有列的编号、名称和数据类型必须在查询实际执行之前为数据库所知执行（即在解析时）。
我发现将东西聚合成一个 JSON 更容易处理。
select customer_number,
jsonb_object_agg(label, value) as props
from the_table
group by customer_number
如果您的前端可以直接处理 JSON 值，您可以到此为止。
如果您真的需要一个每个属性一列的视图，您可以从 JSON 值：
select customer_number,
props ->> 'address' as address,
props ->> 'phone' as phone,
props ->> 'email' as email
from (
select customer_number,
jsonb_object_agg(label, value) as props
from the_table
group by customer_number
) t
我发现添加新属性后这更容易管理。
如果您需要一个包含所有标签的视图，您可以创建一个存储过程来动态创建它。如果不同标签的数量不会经常变化，这可能是一个解决方案：
create procedure create_customer_view()
as
$$
declare
l_sql text;
l_columns text;
begin
select string_agg(distinct format('(props ->> %L) as %I', label, label), ', ')
into l_columns
from the_table;
l_sql :=
'create view customer_properties as
select customer_number, '||l_columns||'
from (
select customer_number, jsonb_object_agg(label, value) as props
from the_table
group by customer_number
) t';
execute l_sql;
end;
$$
language plpgsql;
然后使用以下方法创建视图：
call create_customer_view();
并且在您的代码中只需使用：
select *
from customer_properties;
您可以定期将该过程安排到 运行（例如，通过 Linux 上的 cron 作业）
我有table这样的：
| customer_number | label | value |
|---|---|---|
| 1 | address | St. John 1A |
| 1 | phone | 111111111 |
| 1 | john@cena.com | |
| 2 | address | St. Marry 231A |
| 2 | phone | 222222222 |
| 2 | please@marry.me |
我想要新的 table 或视图，所以它变成了：
| customer_number | address | phone | |
|---|---|---|---|
| 1 | St. John 1A | 111111111 | john@cena.com |
| 2 | St. Marry 231A | 222222222 | please@marry.me |
但将来可能会添加不同的标签，例如可能会有名为 occupation 的新标签。
重要提示，我不知道标签列的值，所以它应该迭代到该列内的任何值。
有什么办法吗？
我使用交叉应用来解决这个问题.. 这是我的查询
select distinct tb9.customer_number, tb9_2.*
from Table_9 tb9 cross apply
(select max(case when tb9_2.[label] like '%address%' then [value] end) as [address],
max(case when tb9_2.[label] like '%phone%' then [value] end) as [phone],
max(case when tb9_2.[label] like '%email%' then [value] end) as [email]
from Table_9 tb9_2
where tb9.customer_number = tb9_2.customer_number
) tb9_2;
一般来说SQL不擅长动态旋转
这是一个将为您转换数据的查询。但是，它不是动态的，即如果添加了未来的 occupation 标签，那么您将不得不更改查询。不确定是否可以接受：
select customer_number,
max(value) filter (where label='address') as address,
max(value) filter (where label='phone') as phone,
max(value) filter (where label='email') as email
from your_customer_table
group by customer_number
假设您是 运行 Postgres 9.4 或更高版本，以便支持 filter 功能。如果不是，则可以使用 case 语句重新处理它：
select customer_number,
max(case when label='address' then value else null end) as address,
max(case when label='phone' then value else null end) as phone,
max(case when label='email' then value else null end) as email
from your_customer_table
group by customer_number
您不能拥有“动态”数据透视表，因为查询的所有列的编号、名称和数据类型必须在查询实际执行之前为数据库所知执行（即在解析时）。
我发现将东西聚合成一个 JSON 更容易处理。
select customer_number,
jsonb_object_agg(label, value) as props
from the_table
group by customer_number
如果您的前端可以直接处理 JSON 值，您可以到此为止。
如果您真的需要一个每个属性一列的视图，您可以从 JSON 值：
select customer_number,
props ->> 'address' as address,
props ->> 'phone' as phone,
props ->> 'email' as email
from (
select customer_number,
jsonb_object_agg(label, value) as props
from the_table
group by customer_number
) t
我发现添加新属性后这更容易管理。
如果您需要一个包含所有标签的视图，您可以创建一个存储过程来动态创建它。如果不同标签的数量不会经常变化，这可能是一个解决方案：
create procedure create_customer_view()
as
$$
declare
l_sql text;
l_columns text;
begin
select string_agg(distinct format('(props ->> %L) as %I', label, label), ', ')
into l_columns
from the_table;
l_sql :=
'create view customer_properties as
select customer_number, '||l_columns||'
from (
select customer_number, jsonb_object_agg(label, value) as props
from the_table
group by customer_number
) t';
execute l_sql;
end;
$$
language plpgsql;
然后使用以下方法创建视图：
call create_customer_view();
并且在您的代码中只需使用：
select *
from customer_properties;
您可以定期将该过程安排到 运行（例如，通过 Linux 上的 cron 作业）