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drop stage s3_customer_csv;
create stage s3_customer_csv 
url = 's3://my-s3-data-lake/customer/csv/' 
comment = 'this customer parquet data';
        
desc stage s3_customer_csv;
    
-- lets list the stage to see all the files and path 
list @s3_customer_csv;
    
-- create a csv file format
create file format csv_ff 
    type = 'csv' 
    compression = 'auto' 
    field_delimiter = ',' 
    record_delimiter = '\n' 
    skip_header = 0 
    field_optionally_enclosed_by = '\042' 
    null_if = ('\\N');
        
        
-- select external stage using $ notation
select t.$1, t.$2, t.$3,t.$4, t.$5, t.$6 , t.$7, t.$8 
from 
@s3_customer_csv (file_format => 'csv_ff') t; 
        
-- what if you give one. extra colum in your $ notation
select t.$1, t.$2, t.$3,t.$4, t.$5, t.$6 , t.$7, t.$8, t.$9 
from 
@s3_customer_csv (file_format => 'csv_ff') t; 

     
create or replace external TABLE customer_csv_et (
        CUST_KEY varchar AS (value:c1::varchar),
        NAME varchar AS (value:c2::varchar),
        ADDRESS varchar AS (value:c3::varchar),
        NATION_KEY varchar AS (value:c4::varchar),
        PHONE varchar AS (value:c5::varchar),
        ACCOUNT_BALANCE varchar AS (value:c6::varchar),
        MARKET_SEGMENT varchar AS (value:c7::varchar),
        COMMENT varchar AS (value:c8::varchar)
    )
with location=@s3_customer_csv
auto_refresh = false
file_format = (format_name = csv_ff)
;

-- lets see the extra value column and it is available in json format.
select * from customer_csv_et;


create or replace external TABLE customer_csv_et_dummy (
    )
with location=@s3_customer_csv
auto_refresh = false
file_format = (format_name = csv_ff);

-- select the table
select * from customer_csv_et;

-- fetch the value column and metadata column
select value, metadata$filename from customer_csv_et;

-- select clause
select value, metadata$filename from customer_csv_et where metadata$filename ='customer/csv/customer_003.csv';

-- if you are not sure about the column names etc, then you can simply add a dummy column and check all values
create or replace external TABLE customer_csv_et_dummy (
      col1 varchar AS (value:c1::varchar)
    )
    with location=@s3_customer_csv
    auto_refresh = false
    file_format = (format_name = csv_ff);

    select * from customer_csv_et_dummy;