Combine SQL query with variable

Question

Redshift support export data to CSV by executing this SQL query.

unload ('select * from bhuvi') 
to 's3://bhuvi-bucket/folder//user-data.csv' 
iam_role 'arn:aws:iam::1111111:role/myredshiftrole' 
delimiter '|'  GZIP";

I have different tables and need to export them to different locations. So I have a stored procedure like below. so I can pass the locations in a variable in the future.

CREATE OR REPLACE PROCEDURE test_variable()
 LANGUAGE plpgsql AS
$$
DECLARE
   sql text;
   s3_loc text;
   role text;
   deli text;
   query text;
BEGIN
   sql:='select * from bhuvi';
   s3_loc:='s3://bhuvi-bucket/folder/';
   role:='arn:aws:iam::1111111:role/myredshiftrole';
   deli:='|';
   query := "unload (sql) to 's3_loc/user-data.csv' iam_role 'role';
   execute query;
END
$$;

but somewhere the syntax is wrong. Im not able to find that. When I call this procedure, im getting this below error.

test=# call test_variable();
ERROR:  column "unload (sql) to 's3_loc/user-data.csv' iam_role 'role' " does not exist
CONTEXT:  SQL statement "SELECT  "unload (sql) to 's3_loc/user-data.csv' iam_role 'role' ""
PL/pgSQL function "test_variable" line 12 at assignment
test=#

Answer 1

You can't use double quotes for string literals. Do include a single quote in a string literal, it has to be escaped by doubling them:

query := 'unload (sql) to ''s3_loc/user-data.csv'' iam_role ''role''';

Additionally can't use names of variables from PL/pgSQL in a SQL string. You need to include the content of that variable in the query string you build:

query := 'unload ('||sql||') to '''||s3_loc||'/user-data.csv'' iam_role '''||role||'''';