Easy GraphQL QueryingSQL
This uses the http_client and json extensions to create a (relatively) flexible and easy to use GraphQL reader. This only supports POST, but it'd be pretty easy to change to GET. There are parameters to control what and how the results are extracted into a DuckDB table.
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INSTALL http_client FROM community; LOAD json; LOAD http_client; -- Run a GraphQL query and get back fields with various diagnostics and intermediate values CREATE OR REPLACE MACRO query_graphql(endpoint, query, -- GraphGQL endpoint and query params:=NULL, -- GraphQL parameters headers:=MAP{}, -- HTTP headers (e.g., auth) result_path:='$', -- json_path to use as results result_structure:=NULL, -- json_structure for results or auto detect strict:=true -- Error on failure to transform results ) AS TABLE SELECT response: http_post(endpoint, headers, IF(params IS NULL, {'query': query}, {'query': query, 'params': params})), body: (response->>'body')::JSON, json: body->result_path, structure: IF(result_structure IS NULL, json_structure(json), result_structure), result: IF(strict, from_json_strict(json, structure), from_json(json, structure)); -- Simple helper to extract GraphQL results to a "normal" table CREATE OR REPLACE MACRO read_graphql(endpoint, query, -- Same as above ... params:=NULL, headers:=MAP{}, result_path:='$', result_structure:=NULL, strict:=true, -- ... Same as above unnest_levels:=0 -- Apply unnest this many times to create table ) AS TABLE WITH nested AS ( SELECT [result] AS result FROM query_graphql(endpoint, query, params:=params, headers:=headers, result_path:=result_path, result_structure:=result_structure, strict:=strict) ) SELECT unnest(result, max_depth:=unnest_levels+1) AS result FROM nested; ------------------- Example usage --------------------- FROM read_graphql('https://rickandmortyapi.com/graphql', $$ query Query($name: String) { characters(page: 2, filter: {name: $name}) { info { count } results { id name gender } } } $$, params:={'name': 'Morty'}, result_path:='$.data.characters.results', result_structure:=[{id:'int',name:'string',gender:'string'}], unnest_levels:=2 ); -- Example Results ------------------ -- ┌─────────┬────────────────────┬─────────┐ -- │ id │ name │ gender │ -- │ int32 │ varchar │ varchar │ -- ├─────────┼────────────────────┼─────────┤ -- │ 21 │ Aqua Morty │ Male │ -- ... -- ├─────────┴────────────────────┴─────────┤ -- │ 20 rows 3 columns │ -- └────────────────────────────────────────┘
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DuckDB to geojsonSQL
Snippet helps put correctly formatted geojson file using spatial and json extensions from any table/query.
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COPY ( SELECT *, -- all these field will become properties in resulting geojson (doesnt work well with map-like columns) ST_GeomFromText(wkt) as geometry -- this is the main geometry entry FROM temp_table ) TO 'test.geojson' WITH (FORMAT GDAL, DRIVER 'GeoJSON', LAYER_NAME 'test');
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Export/import/share DuckDB UI Notebooks
The DuckDB UI stores notebook content in an internal database called _duckdb_ui. You can query and export notebook content, as well as insert new definitions into the database. Warning: Modifying the internal database may lead to corruption and data loss. Be cautious and use it at your own risk!
Export a notebook definition to JSONSQL
copy ( select "json" from _duckdb_ui.notebook_versions where 1=1 and title = 'MySingleNotebook' and expires is null ) to 'exported-notebook.json'
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Import notebook definitionSQL
set variable notebook_content = (select json from 'exported-notebook.json'); set variable notebook_id = uuid(); set variable current_timestamp = now(); begin transaction; insert into _duckdb_ui.notebooks (id, name, created) select getvariable('notebook_id'), 'notebook_' || getvariable('notebook_id'), getvariable('current_timestamp') ; insert into _duckdb_ui.notebook_versions (notebook_id, version, title, json, created, expires) select getvariable('notebook_id'), 1, 'imported-notebook-' || getvariable('current_timestamp'), getvariable('notebook_content'), getvariable('current_timestamp'), null ; commit;
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Detect Schema Changes Across Datasets (Python)Python
Compare the schema of two datasets and identify any differences.
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import duckdb def compare_schemas(file1, file2): """ Compare schemas of two datasets and find differences. Args: file1 (str): Path to the first dataset (CSV/Parquet). file2 (str): Path to the second dataset (CSV/Parquet). Returns: list: Schema differences. """ con = duckdb.connect() schema1 = con.execute(f"DESCRIBE SELECT * FROM read_csv_auto('{file1}')").fetchall() schema2 = con.execute(f"DESCRIBE SELECT * FROM read_csv_auto('{file2}')").fetchall() return {"file1_schema": schema1, "file2_schema": schema2} # Example Usage differences = compare_schemas("data1.csv", "data2.csv") print(differences)
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Remove Duplicate Records from a CSV File (Bash)Bash
This function helps clean up a dataset by identifying and removing duplicate records. It’s especially useful for ensuring data integrity before analysis.
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#!/bin/bash function remove_duplicates() { input_file="$1" # Input CSV file with duplicates output_file="$2" # Deduplicated output CSV file # Use DuckDB to remove duplicate rows and write the cleaned data to a new CSV file. duckdb -c "COPY (SELECT DISTINCT * FROM read_csv_auto('$input_file')) TO '$output_file' (FORMAT CSV, HEADER TRUE);" } #Usage remove_duplicates "input_data.csv" "cleaned_data.csv"
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Query JSON files Using SQL in PythonPython
DuckDB supports querying JSON files directly, enabling seamless analysis of semi-structured data. This script lets you apply SQL queries to JSON files within a Python environment, ideal for preprocessing or exploring JSON datasets.
Execute this Python
import duckdb def query_json(file_path, query): """ Query JSON data directly using DuckDB. Args: file_path (str): Path to the JSON file. query (str): SQL query to execute on the JSON data. Returns: pandas.DataFrame: Query results as a Pandas DataFrame. """ con = duckdb.connect() # Execute the query on the JSON file and fetch the results as a Pandas DataFrame. df = con.execute(f"SELECT * FROM read_json_auto('{file_path}') WHERE {query}").df() return df # Example Usage result = query_json("./json/query_20min.json", "scheduled = true") print(result)
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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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