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- QUALIFY Clause 13622
- The QUALIFY clause is used to filter the results of WINDOW functions . This filtering of results is similar to how a HAVING clause filters the results of aggregate functions applied based on the GROUP BY clause . The QUALIFY clause avoids t
...he need for a subquery or WITH clause to perform this filtering (much like HAVING avoids a subquery). An example using a WITH clause instead of QUALIFY is included below the QUALIFY examples. Note that this is f... - https://man.mtool.work/duckdb/2.0/sql/query_syntax/qualify.html
- Quack Remote Protocol 10118
- The Quack extension turns a DuckDB instance into a server that other DuckDB instances (clients) can connect to over HTTP. This page covers the protocol at a glance and walks through basic usage on both sides of the wire. For the full list o
...ponses are encoded with DuckDB's internal serialization primitives (the same code path used by the Write-Ahead Log ). This avoids round-tripping data through an interchange format and keeps complex types (nested, decimals, intervals, ...) lossless acro...ough the httpfs HTTP client, which caches connections by default ( httpfs_connection_caching = true ). Reusing connections avoids a new TCP and, with SSL, a costly TLS handshake per request. To open a fresh connection for every request (e.g., for debug... - https://man.mtool.work/duckdb/2.0/quack/overview.html
- Instantiate 9242
- Overview DuckDB-Wasm can be instantiated in several ways, depending on how your application bundles and serves its assets. Each approach resolves the mainModule (the WebAssembly file) and the mainWorker (the worker script) for the browser's
...erformance; DuckDB and DuckDB-Wasm are written in C++ and use exceptions to propagate errors, so native exception handling avoids emulating them through JavaScript coi — adds threading for parallel query execution; it requires the page to be cross-orig...'opfs://export.csv'`); Automatic registration is convenient for one-off reads. Manual registration requires more code but avoids re-acquiring an OPFS access handle on every statement, which adds up for applications that run many small queries. Note OP... - https://man.mtool.work/duckdb/2.0/clients/wasm/instantiation.html
- Timestamp Issues 8795
- Timestamp with Time Zone Promotion Casts Working with time zones in SQL can be quite confusing at times. For example, when filtering to a date range, one might try the following query: SET timezone = 'America/Los_Angeles'; CREATE TABLE time
...ng the parts one by one because the underlying binning computation computes all parts, so picking out the ones in the list avoids duplicate time zone conversions. Also notice that we are leveraging the DATE cast rules from the previous section to bound... - https://man.mtool.work/duckdb/2.0/guides/sql_features/timestamps.html
- Handle Results 8366
- Overview Beyond the standard JDBC ResultSet , the DuckDB driver can hand results to Apache Arrow , stream large results instead of materializing them, and expose raw columnar data chunks. This page covers each of these result-handling optio
...data chunks via the org.duckdb.DuckDBChunkedResult class. This exposes the C API's duckdb_fetch_chunk function to Java and avoids the per-row overhead required by the JDBC ResultSet interface. Chunk contents are read through the same DuckDBDataChunkRea... - https://man.mtool.work/duckdb/2.0/clients/java/result_handling.html
- Import Data 8366
- Overview The Rust client offers two ways to get data into DuckDB in bulk: the high-performance Appender for inserting rows from Rust, and reading directly from data files such as Parquet, CSV, and JSON. Both are described below. Appender Th
...ing Arrow Data With the appender-arrow feature enabled, an Appender can append an Apache Arrow RecordBatch directly, which avoids building a parameter list per row. See Handle Results for the Arrow integration. Reading Data Files DuckDB can read many f... - https://man.mtool.work/duckdb/2.0/clients/rust/data_import.html
- Environment 8366
- The environment where DuckDB is run has an obvious impact on performance. This page focuses on the effects of the hardware configuration and the operating system used. Hardware Configuration CPU DuckDB's officially supported architectures a
...the data in immutable Parquet files on object storage and the transactional metadata in a separate catalog database, which avoids the concurrent read-write access patterns on a single large file that network-attached storage handles poorly. Operating S... - https://man.mtool.work/duckdb/2.0/guides/performance/environment.html
- Run Queries 7919
- Overview Because the Go client implements database/sql , queries run through the standard methods: Exec and ExecContext send statements that do not return rows, such as INSERT or DDL, and report the number of affected rows. Query , QueryCon
...ws", n) Binding Parameters Values are bound to a statement's placeholders rather than formatted into the SQL string, which avoids SQL injection and lets DuckDB reuse a plan. DuckDB accepts positional ( ? ) and numbered ( $1 , $2 ) placeholders; pass th... - https://man.mtool.work/duckdb/2.0/clients/go/querying.html
- Import Data 7919
- Overview The JDBC driver offers two ways to load data into DuckDB in bulk: the high-performance Appender and a JDBC batch writer. This page describes both and when to use each. Appender The Appender is available in the DuckDB JDBC driver vi
...inline, without parameters. Queue each statement with addBatch(String) and submit them together with executeBatch() . This avoids parameter binding but does not benefit from the reuse that prepared statements provide. import java.sql.DriverManager; imp... - https://man.mtool.work/duckdb/2.0/clients/java/data_import.html
- Window Functions 6596
- DuckDB supports window functions , which can use multiple rows to calculate a value for each row. Window functions are blocking operators , i.e., they require their entire input to be buffered, making them one of the most memory-intensive o
...already evaluated, so it's not possible to use these clauses to filter the results of window functions The QUALIFY clause avoids the need for a subquery or WITH clause to perform this filtering. Box and Whisker Queries All aggregates can be used as wi... - https://man.mtool.work/duckdb/2.0/sql/functions/window_functions.html
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