BigQuery: Loop through tables in dataset and drop tables with a specific prefix - google-bigquery

Question

Our development environment in BigQuery is isolated to a development dataset i.e. dev in BigQuery. The environments are further isolated by a prefix of the ticket for each table i.e. DATA-100-change-table would correspond to the DATA-100 ticket.
I am aware of setting TTL for BigQuery, however, I am also interested in having a query I could run by hand to delete the tables.
So far, I have the below:
begin
-- Create temporary table of tables to drop from `dev` with prefix
create temp table to_drop (drop_string STRING)
as
(
select concat("drop table if exists ", table_catalog, ".", table_schema, ".", table_name)
from dev.INFORMATION_SCHEMA.TABLES
where table_name like "DATA-100%"
);
-- Loop through table and execute drop_string statements
for drop_statement in (select drop_string from to_drop)
do
execute immediate drop_statement;
end for;
end
However, this fails with the following error:
Query error: Cannot coerce expression drop_statement to type STRING at [14:23]
Is my approach right here? How do I best delete all tables with a prefix in BigQuery?
Also, if possible, I would like this query to handle views as well.

Answer 1

The variable drop_statement in the for loop contains a struct. So you have to access the string with drop_statement.drop_string.
begin
-- Create temporary table of tables to drop from `dev` with prefix
create temp table to_drop (drop_string STRING)
as
(
select concat("drop table if exists ", table_catalog, ".", table_schema, ".", table_name)
from dev.INFORMATION_SCHEMA.TABLES
where table_name like "DATA-100%" and table_type = 'BASE TABLE'
);
-- Loop through table and execute drop_string statements
for drop_statement in (select drop_string from to_drop)
do
execute immediate drop_statement.drop_string;
end for;
end
To drop VIEWs, just replace table_type = "BASE TABLE" with table_type = "VIEW" and use drop view if exists instead.

Answer 2

Using p13rr0m's answer as inspiration, I've come up with the below:
begin
create temp table to_drop (drop_string STRING)
as
(
select
case
when table_type = "BASE TABLE" then concat("drop table if exists `", table_catalog, ".", table_schema, ".", table_name, "`")
when table_type = "VIEW" then concat("drop view if exists `", table_catalog, ".", table_schema, ".", table_name, "`")
end as drop_string
from
`dev.INFORMATION_SCHEMA.TABLES`
where
table_name like "DATA_100%"
);
for drop_statement in (select drop_string from to_drop)
do
execute immediate drop_statement.drop_string;
end for;
end
Had to add backticks to the tables as it was failing on dropping views.