如何在postgresql中将语句结果复制到本地

Question

我有以下 with 语句和复制命令

with output01 as
(select * from (
select name,
case
    when column1 is not null and lower(column1) in ('point1','point2','point3','point4') then 3456
    else null end column1Desc,
case
    when column2 is not null and lower(column2) in ('point1','point2','point3','point4') then 2456
    else null end column2Desc,
column3, column4),
output02 as
(select * from (
select name,
case
    when column1 is not null and lower(column1) in ('point1','point2','point3','point4') then 3456
    else null end column1Desc,
case
    when column2 is not null and lower(column2) in ('point1','point2','point3','point4') then 2456
    else null end column2Desc,
column3, column4),
output3 as (SELECT * FROM output01 UNION ALL SELECT * FROM output02)

\copy (select * from output3) to '/usr/share/output.csv' with CSV ENCODING 'UTF-8' DELIMITER ',' HEADER;

我遇到以下错误

ERROR: relation "tab3" does not exist

Answer 1

您收到此错误是因为您在不同的语句中运行您的 CTE 查询和 copy 命令。考虑到您的 with 查询工作正常，您应该像下面这样编写 copy 语句：

\copy (WITH tab1 as (Your SQL statement),
tab2 as ( SELECT ... FROM tab1 WHERE your filter),
tab3 as ( SELECT ... FROM tab2 WHERE your filter)
SELECT * FROM tab3) to '/usr/share/results.csv' with CSV ENCODING 'UTF-8' DELIMITER ',' HEADER;

Answer 2

所有 psql 反斜杠命令都需要写在一行中，因此您不能将 multi-line 查询与 \copy 一起使用。唯一的解决方法是使用该查询创建一个（临时）视图，然后在 \copy 命令中使用它。

大致情况：

create temporary view data_to_export
as
with cte as (..)
select * 
from cte
;

\copy (select * data_to_export) to ...

如何在postgresql中将语句结果复制到本地

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