可读外部表（不可以做dml操作）

可写外部表（只insert,不可以select,update,delete）

创建外部表

=# CREATE EXTERNAL WEB TABLE ext_expenses (name text,
date date, amount float4, category text, description text)
LOCATION ( 'http://intranet.company.com/expenses/sales/file.csv',
'http://intranet.company.com/expenses/exec/file.csv',
'http://intranet.company.com/expenses/finance/file.csv',
'http://intranet.company.com/expenses/ops/file.csv',
'http://intranet.company.com/expenses/marketing/file.csv',
'http://intranet.company.com/expenses/eng/file.csv' )
FORMAT 'CSV' ( HEADER );

装载外部表数据

=# INSERT INTO expenses_travel
SELECT * from ext_expenses where category='travel';
或者想要快速装载全部数据到一个新的数据库表中：
=# CREATE TABLE expenses AS SELECT * from ext_expenses;

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