Dynamic SQL with EXECUTE and nested format() - postgresql

Question

I tried doing this with just a normal CTE (no EXECUTE ... FORMAT) and I was able to do it.
I basically have a table that has some 5 columns and some data in each column that I wanted to concatenate and such to manifest/generate some data in a new column.
I can do something like this and it works:
WITH cte AS (SELECT *, case
when var1 = '' then ''
when var2 = '' then ''
else '' end, 'adding_dummy_text_column'
FROM some_other_table sot
WHERE sot.type = 'java')
INSERT INTO my_new_table
SELECT *, 'This is the new column I want to make with some data from my CTE' || c.type
FROM cte c;
So this works as I said. I'll end up getting a new table that has an extra column which a hardcoded, concatenated string This is the new column I want to make with some data from my CTE Java
Of course, whatever is in the c.type column for the corresponding row in the CTE as it loads the SELECT is what gets concatenated to that string.
The problem is, as soon as I start using the EXECUTE...FORMAT to make it cleaner and have more power to concatenate/combined different data pieces from my different columns (I have data kind of scattered around in bad formats and I'm populating a fresh new table), it's as if the FORMAT arguments or the variables cannot detect the CTE table.
This is how I'm doing it
EXECUTE FORMAT ('WITH cte AS (SELECT *, case
when var1 = %L then %L
when var2 = '' '' then '' ''
else '' '' end, ''adding_dummy_text_column''
FROM some_other_table sot
WHERE sot.type = ''java'')
INSERT INTO my_new_table
SELECT *, ''This is the new column I want to make with some data from my CTE %I''
FROM cte c', 'word1', 'word2', c.type
);
OK, so I know I used the empty string '' '' in this example and the %L but i just wanted to show I had no issues with any of that. Its when I try to reference my CTE columns, so you can see I'm trying to do the same concatenation but by leveraging the EXECUTE...FORMAT and using the %I identifiers. So, the first 2 args are just fine, its the c.type that just no matter what column I try, doesn't work. Also, I removed the c alias and didn't get any better luck. It's 100% anytime I reference the columns on the CTE though, as I have removed all that code and it runs just fine without that.
But yeah, is there any work around? I really want to transform some data and now have to do the || for concatenation.

Answer 1

This should do it:
EXECUTE format($f$WITH cte AS (SELECT *, CASE
WHEN var1 = %L THEN %L
WHEN var2 = ' ' THEN ' '
ELSE ' ' END, 'adding_dummy_text_column'
FROM some_other_table sot
WHERE sot.type = 'java')
INSERT INTO my_new_table
SELECT *, format('This is the new column I want to make with some data from my CTE %%I', c.type)
FROM cte c$f$
, 'word1', 'word2');
There are two levels. You need a second format() that's executed by the dynamic SQL string that's been concatenated by the first format().
I simplified with dollar-quoting. See:
Insert text with single quotes in PostgreSQL
The nested % character must be escaped by doubling it up: %%I. See:
What does %% in PL/pgSQL mean?
Generates and executes this SQL statement:
WITH cte AS (SELECT *, CASE
WHEN var1 = 'word1' THEN 'word2'
WHEN var2 = ' ' THEN ' '
ELSE ' ' END, 'adding_dummy_text_column'
FROM some_other_table sot
WHERE sot.type = 'java')
INSERT INTO my_new_table
SELECT *, format('This is the new column I want to make with some data from my CTE %I', c.type)
FROM cte c
Which could be simplified and improved to this equivalent:
INSERT INTO my_new_table(co1, col2, ...) -- provide target column list!
SELECT *
, CASE WHEN var1 = 'word1' THEN 'word2'
WHEN var2 = ' ' THEN ' '
ELSE ' ' END
, 'adding_dummy_text_column'
, format('This is the new column I want to make with some data from my CTE %I', sot.type)
FROM some_other_table sot
WHERE sot.type = 'java'
About the missing target column list:
Cannot create stored procedure to insert data: type mismatch for serial column

Answer 2

You can one command, create and insert into new table!
create table my_new_table as
select *
, CASE WHEN var1 = 'hello' THEN 'word2'
WHEN var2 = ' ' THEN 'var2 is empty'
ELSE ' ' END adding_dummy_text_column
, format(
'This is the new column I want to make with some data from my CTE %I', sot.type)
from some_other_table sot
where sot.type ='java';