PostgreSQL，使用查询删除表 [英] PostgreSQL, drop tables with query

问题描述

我有这样的查询来列出当前数据库中的表：

I have such query to list tables in current database:

SELECT c.relname 
FROM pg_catalog.pg_class c 
LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace 
WHERE c.relkind 
IN ('r','') AND n.nspname NOT IN ('pg_catalog', 'pg_toast') AND
pg_catalog.pg_table_is_visible(c.oid)

使用子查询之类的上层SELECT删除所有这些表：

I am trying to drop all those tables using upper SELECT like subquery:

DROP TABLE IF EXISTS (SELECT c.relname 
FROM pg_catalog.pg_class c 
LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace 
WHERE c.relkind 
IN ('r','') AND n.nspname NOT IN ('pg_catalog', 'pg_toast') AND
pg_catalog.pg_table_is_visible(c.oid)) as tname 

但是那不起作用。

如何正确编写一个查询，该查询将删除显示的SELECT查询列出的所有表？

现在我使用DataReader遍历查询结果将表拖放一个。

但是我认为这可能会一次。

But that don't work.
How to propery write a query which will drop all tables listed by showed SELECT query?
For now I use DataReader for loop through query result and drop tables by one.
But I think that may go 'at once'.

推荐答案

您需要为此使用动态SQL， turn只能用于PL / pgSQL之类的过程语言，如下所示：

You need to use dynamic SQL for this, which in turn can only be used in a procedural language like PL/pgSQL, something like this:

do
$$
declare
   stmt text;
   table_rec record;
begin
   for table_rec in (SELECT c.relname as tname
                     FROM pg_catalog.pg_class c 
                       LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace 
                     WHERE c.relkind IN ('r','') 
                       AND n.nspname NOT IN ('pg_catalog', 'pg_toast') 
                       AND pg_catalog.pg_table_is_visible(c.oid))
   loop
     execute 'drop table '||table_rec.tname||' cascade';
   end loop;
end;
$$

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