Create Temp Table in Each Loop and Union After Loop Completion - google-bigquery

Question

Using BigQuery's standard SQL scripting functionality, I want to 1) create a temp table for each iteration of a loop, and 2) union those temp tables after the loop is complete. I've tried something like the following:
DECLARE i INT64 DEFAULT 1;
DECLARE ttable_name STRING;
WHILE i < 10 DO
SET ttable_name = CONCAT('temp_table_', CAST(i AS STRING));
CREATE OR REPLACE TEMP TABLE ttable_name AS
SELECT * FROM my_table AS mt WHERE mt.my_col = 1;
SET i = i + 1;
END LOOP;
SELECT * FROM temp_table_*; -- wildcard table to union all results
But I get the following error:
Exceeded rate limits: too many table update operations for this table.
How can I accomplish this task?

Answer 1

Your script does not work the way you think it does!
Instead of writing in each iteration into separate table named like temp_table_N - you actually writing to the very same temp table named ttable_name - thus the Exceeded rate limits error
BigQuery does not allow using variables for objects names

Answer 2

Don't create new tables. Add to an existing one with an INSERT INTO, or hold data in a variable (if it's not too much data), as in:
DECLARE steps INT64 DEFAULT 1;
DECLARE table_holder ARRAY<STRUCT<steps INT64, x INT64, y ARRAY<INT64>>>;
LOOP
SET table_holder = (
SELECT ARRAY_AGG(
STRUCT(steps, 1 AS x, [1,2,3] AS y))
FROM (SELECT '')
);
SET steps = steps+1;
IF steps=30 THEN LEAVE; END IF;
END LOOP;
CREATE TABLE temp.results
AS
SELECT *
FROM UNNEST(table_holder)
Related: https://stackoverflow.com/a/59314390/132438

Answer 3

Question asker/OP here. While I have selected #felipe-hoffa's answer as I believe it will be best for future readers of this question, I have actually gone a different route in solving my problem:
BEGIN
DECLARE i INT64 DEFAULT 1;
CREATE OR REPLACE TEMP TABLE ttable AS
SELECT
CAST(NULL AS INT64) AS col1 -- cast NULL as the type of target col
,CAST(NULL AS FLOAT64) AS col2
,CAST(NULL AS DATE) AS col3;
WHILE i < 10 DO
-- overwrite `ttable` with its previous contents union'ed
-- with new data results from current loop iteration
CREATE OR REPLACE TEMP TABLE ttable AS
SELECT mt.col1, mt.col2, mt.col3 FROM my_table AS mt WHERE mt.other_col = i
UNION ALL
SELECT * FROM ttable;
SET i = i + 1;
END LOOP;
SELECT * FROM ttable; -- UNION'ed results
DROP TABLE IF EXISTS ttable;
END;
Why? I find it easier to stay in "table land" than to venture into "STRUCT/ARRAY land".