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76 lines
1.6 KiB
Markdown
76 lines
1.6 KiB
Markdown
# DuckDB
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Arguments are defined with comments and used with `$name` syntax:
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```sql
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-- $name (text) = default
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-- $age (integer)
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SELECT * FROM users WHERE name = $name AND age > $age;
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```
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## Ducklake Integration
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Attach Ducklake for data lake operations:
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```sql
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-- Main ducklake
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ATTACH 'ducklake' AS dl;
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-- Named ducklake
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ATTACH 'ducklake://my_lake' AS dl;
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-- Then query
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SELECT * FROM dl.schema.table;
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```
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## External Database Connections
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Connect to external databases using resources:
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```sql
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ATTACH '$res:path/to/resource' AS db (TYPE postgres);
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SELECT * FROM db.schema.table;
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```
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## S3 File Operations
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Read files from S3 storage:
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```sql
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-- Default storage
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SELECT * FROM read_csv('s3:///path/to/file.csv');
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-- Named storage
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SELECT * FROM read_csv('s3://storage_name/path/to/file.csv');
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-- Parquet files
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SELECT * FROM read_parquet('s3:///path/to/file.parquet');
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-- JSON files
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SELECT * FROM read_json('s3:///path/to/file.json');
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```
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### Receiving an S3Object as a script parameter
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Declare the arg with type `(s3object)`. Windmill renders an S3 file picker for it
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and binds the arg as the bare `s3://storage/key` URI, which DuckDB's reader
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functions consume directly:
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```sql
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-- $file (s3object)
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SELECT * FROM read_parquet($file);
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```
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Works with any DuckDB reader: `read_csv($file)`, `read_json($file)`, etc.
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### Writing query results to S3
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DuckDB writes to S3 natively via `COPY ... TO`:
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```sql
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COPY (SELECT * FROM users) TO 's3:///exports/users.parquet' (FORMAT PARQUET);
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```
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Use this instead of the `-- s3` streaming directive supported by the other SQL
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dialects — that directive is not available in DuckDB.
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