PostgreSQL, drop tables with query

Question

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.relnames         


        

Answer 1

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

Answer 2

You can "generate" your DROP statement using a SELECT statement. For example:

SELECT 'DROP TABLE "' + table_name + '"' 
FROM information_schema.tables
WHERE table_name LIKE '[your_prefix_here]%'

(Replace '[your_prefix_here]%' with your conditions and wild cards)