cursor for loop & dynamic SQL - Snowflake - sql

Question

I'm attempting to write a procedure that takes in a list of tables and date_column to create some row_counts by calendar dates for reconciliation purposes.
SELECT t.*
FROM (
VALUES ('tbl1', 'created_date')
, ('tbl2', 'modify_date')
, ('tbl3', 'last_seen_date')
) t(tbl, dt)
+----+--------------+
|TBL |DT |
+----+--------------+
|tbl1|created_date |
|tbl2|modify_date |
|tbl3|last_seen_date|
+----+--------------+
I'm connected to Snowflake via a JDBC connection using Datagrip - so I assume I need to follow the classic SnowSQL part of the documentation:
https://docs.snowflake.com/en/developer-guide/snowflake-scripting/loops.html#cursor-based-for-loops
EXECUTE IMMEDIATE $$
DECLARE
dt text
, tbl text;
c1 CURSOR FOR SELECT dt, tbl from t;
BEGIN
FOR record in c1 DO
dt := record.dt
tbl := record.tbl
stmt =: 'SELECT COUNT(*)' ||
CONCAT(', DAYOFMONTH(', $dt, ')') ||
CONCAT('\n FROM ', $tbl) ||
CONCAT('\n WHERE YEAR(', $dt, ')', ' = YEAR(CURRENT_DATE)') ||
CONCAT('\n AND MONTH(', $dt, ')', ' = MONTH(CURRENT_DATE)') ||
'\n GROUP BY' ||
CONCAT('\n DAYOFMONTH(', $dt, ')')
EXECUTE IMMEDIATE stmt -- will adapt this to be an update statement eventually.
END FOR
end;
$$
This returns a SQL Compilation error, I've tried a few different variations of this but I'm none the wiser on how to proceed.

Answer 1

Instead of concatenating the query string which makes it almost unreadable it could be rewritten using bind variables:
DECLARE
dt text;
tbl text;
stmt text;
c1 CURSOR FOR SELECT dt, tbl from t;
BEGIN
FOR record in c1 DO
dt := record.dt;
tbl := record.tbl;
stmt := 'INSERT INTO result(cnt, day_of_month)
SELECT COUNT(*), DAYOFMONTH(IDENTIFIER(?)) AS day_of_month
FROM TABLE(?)
WHERE YEAR(IDENTIFIER(?)) = YEAR(CURRENT_DATE)
AND MONTH(IDENTIFIER(?)) = MONTH(CURRENT_DATE)
GROUP BY day_of_month';
EXECUTE IMMEDIATE :stmt USING (dt, tbl, dt, dt);
RETURN stmt;
END FOR;
END;
If column or table is parameter it should be wrapped with IDENTIFIER/TABLE funtion.
For sample data:
CREATE OR REPLACE TABLE t AS
SELECT 'col1' AS dt, 'tab1' AS tbl UNION ALL
SELECT 'col2' AS dt, 'tab1' ;
CREATE TABLE tab1(col1 DATE, col2 DATE) AS
SELECT CURRENT_DATE(), CURRENT_DATE()-40;
CREATE TABLE result(cnt INT, day_of_month INT);
SELECT * FROM result;

Answer 2

There are lots of minor issues like missing semicolons etc. Here is the fixed script:
DECLARE
dt text;
tbl text;
stmt text;
c1 CURSOR FOR SELECT dt, tbl from t;
BEGIN
FOR record in c1 DO
dt := record.dt;
tbl := record.tbl;
stmt := 'SELECT COUNT(*)' ||
CONCAT(', DAYOFMONTH(', dt, ')') ||
CONCAT('\n FROM ', tbl) ||
CONCAT('\n WHERE YEAR(', dt, ')', ' = YEAR(CURRENT_DATE)') ||
CONCAT('\n AND MONTH(', dt, ')', ' = MONTH(CURRENT_DATE)') ||
'\n GROUP BY' ||
CONCAT('\n DAYOFMONTH(', dt, ')');
-- EXECUTE IMMEDIATE :stmt;
RETURN stmt;
END FOR;
END;