将 csv 文件的几列复制到表格中 [英] Copy a few of the columns of a csv file into a table
问题描述
我有一个包含 10 列的 CSV 文件.创建 4 列 PostgreSQL 表后,我想将 10 列中的一些复制到表中.
I have a CSV file with 10 columns. After creating a PostgreSQL table with 4 columns, I want to copy some of 10 columns into the table.
我的 CSV 表的列如下:
the columns of my CSV table are like:
x1 x2 x3 x4 x5 x6 x7 x8 x9 x10
我的 PostgreSQL 表的列应该是这样的:
the columns of my PostgreSQL table should be like:
x2 x5 x7 x10
推荐答案
如果是临时任务
用输入文件中的所有列创建一个临时表
If it is an ad hoc task
Create a temporary table with all the columns in the input file
create temporary table t (x1 integer, ... , x10 text)
从文件复制到其中:
copy t (x1, ... , x10)
from '/path/to/my_file'
with (format csv)
现在从临时表插入最终表:
Now insert into the definitive table from the temp:
insert into my_table (x2, x5, x7, x10)
select x2, x5, x7, x10
from t
然后放下它:
drop table t
如果是频繁的任务
使用 file_fdw
扩展.作为超级用户:
If it is a frequent task
Use the file_fdw
extension. As superuser:
create extension file_fdw;
create server my_csv foreign data wrapper file_fdw;
create foreign table my_csv (
x1 integer,
x2 text,
x3 text
) server my_csv
options (filename '/tmp/my_csv.csv', format 'csv' )
;
将表的选择权限授予将要读取它的用户:
Grant select permission on the table to the user who will read it:
grant select on table my_csv to the_read_user;
然后在必要时直接从 csv 文件中读取,就像它是一个表格一样:
Then whenever necessary read directly from the csv file as if it were a table:
insert into my_table (x2)
select x2
from my_csv
where x1 = 2
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