SQL, Python & More for DuckDB - Page 3

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read_dsv() -> Parse properly separated CSV files

I tend to prefer using the ASCII unit (\x1f) and group separator (\x1e) as resp. column and line delimiters in CSVs (which technically no longer makes them a CSV). The read_csv function doesn't seem to want to play nice with these, so here's my attempt at a workaround.

Marco definitionSQL

-- For more info on DSVs (I'm not the author): https://matthodges.com/posts/2024-08-12-csv-bad-dsv-good/
CREATE OR REPLACE MACRO read_dsv(path_spec)
 AS TABLE
(
with _lines as (
    select 
        filename
        ,regexp_split_to_array(content, '\x1e') as content
    from read_text(path_spec )
)
, _cleanup as (
    select 
        filename
        ,regexp_split_to_array(content[1],'\x1f') as header
        ,generate_subscripts(content[2:],1) as linenum
        ,unnest((content[2:]).list_filter(x -> trim(x) != '').list_transform(x -> x.regexp_split_to_array('\x1f'))) as line
    from _lines
)
select
    filename
    ,linenum
    ,unnest(map_entries(map(header, line)), recursive := true) as kv
from _cleanup
);
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UsageSQL

-- You can use the same path specification as you would with read_text or read_csv, this includes globbing.
-- Trying to include the pivot statement in the macro isn't possible, as you then have to explicitly define the column values (which defeats the purpose of this implementation)
pivot read_dsv("C:\Temp\csv\*.csv")
on key
using first(value)
group by filename, linenum
order by filename, linenum
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DuckØ

Created 11/30/24

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Read Apache Iceberg to Google SheetsSQL

Sometimes you just need to get an Apache Iceberg table into Google Sheets for further analysis. The 'gsheet_id' can be found in the URL of your Google Sheet, and writes to the sheet with gid=0.

Execute this SQL

-- get iceberg extension
INSTALL iceberg;
LOAD iceberg;
-- get gsheets extension
INSTALL gsheets FROM community;
LOAD gsheets;
-- authenticate to google sheets
CREATE SECRET (TYPE gsheet);
-- copy the iceberg data to your google sheet!
COPY (from iceberg_scan('s3://my-bucket/iceberg_table')) TO ‘gsheet_id’ (FORMAT gsheet);
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Jacob Matson

Created 11/22/24

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Label columns based on source tableSQL

Commonly, tables that are joined together have overlapping column names. This snippet will rename all columns to have a prefix based on the source table. No more duplicate names! This is similar to the Pandas join feature of lsuffix and rsuffix.

Execute this SQL

SELECT 
    COLUMNS(t1.*) AS 't1_\0',
    COLUMNS(t2.*) AS 't2_\0'
FROM range(10) t1 
JOIN range(10) t2 ON t1.range = t2.range
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Alex Monahan

Created 11/21/24

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Generate series of numbers in DuckDB

DuckDB has two common ways to generate a series of numbers: the range() function and the generate_series() function. They differ only in that the generate_series() function has a 'stop' value that's inclusive, while the 'stop' value of range() is exclusive.

generate_series with inclusive stop valueSQL

// generate_series(start, stop, step)
// get all even numbers, starting at 0 up to and including 100
SELECT * FROM generate_series(0,100,2);
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range with exclusive stop valueSQL

// range(start, stop, step)
// get all even numbers, starting at 0 up to and including 98
SELECT * FROM range(0,100,2);
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Generate range() as arraySQL

// Using range() as a column value instead of a table
// in your SQL statement will return an array of the
// numbers in the range
SELECT range(0,100,2)
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Ryan Boyd

Created 11/02/24

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Run SQL file in DuckDB CLI

The DuckDB CLI enables you to execute a set of SQL statements stored in a file or passed in via STDIN. There are a few variants of this capability demonstrated below.

Read and execute SQL using init CLI argument and prompt for additional SQL statementsBash

# executes SQL in create.sql, and then prompts for additional 
# SQL statements provided interactively. note that when specifying
# an init flag, the ~/.duckdbrc file is not read
duckdb -init create.sql
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Read and execute SQL using init CLI argument and immediately exit Bash

# executes SQL in create.sql and then immediately exits
# note that we're specifying a database name so that we
# can access the created data later. note that when specifying
# an init flag, the ~/.duckdbrc file is not read
duckdb -init create.sql -no-stdin mydb.ddb
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Pipe SQL file to the DuckDB CLI and exitBash

duckdb < create.sql mydb.ddb
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Ryan Boyd

Edited 11/02/24