COPY命令：仅复制csv中的特定列 [英] COPY command: copy only specific columns from csv

问题描述

我对PostgreSQL中的 COPY 命令有个疑问。我有一个CSV文件，我只想将一些列值复制到PostgreSQL表中。

I had a question surrounding the COPY command in PostgreSQL. I have a CSV file that I only want to copy some of the columns values into my PostgreSQL table.

是否可以这样做？我熟悉使用 COPY 命令将CSV中的所有数据复制到表格中，并使用标题映射到列名称，但是如果仅在我想要一些列？

Is it possible to do this? I am familiar with using the COPY command to copy all of the data from a CSV into a table using the header to map to the column names but how is this possible when I only want some of the columns?

推荐答案

预处理CSV文件或（我可能会这样做）导入到目标表的临时副本和第二步中的 INSERT 仅选定的列：

Either pre-process the CSV file, or (what I probably would do) import into a temporary copy of the target table and INSERT only selected columns in a second step:

CREATE TEMP TABLE tmp AS SELECT * FROM target_table LIMIT 0;
ALTER TABLE tmp ADD COLUMN etra_column1 text
             ,  ADD COLUMN etra_column2 text;  -- add excess columns
COPY tmp FROM '/path/tp/file.csv';

INSERT INTO target_table (col1, col2, col3)
SELECT col1, col2, col3 FROM tmp  -- only reelvant columns
WHERE  ...  -- optional, to also filter rows

临时表会在会话结束时自动删除。如果处理时间较长，请使用常规表。

A temporary table is dropped automatically at the end of the session. If the processing takes longer, use a regular table.

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