The first step to using a database system is to insert data into that system. DuckDB provides several data ingestion methods that allow you to easily and efficiently fill up the database. In this section, we provide an overview of these methods so you can select which one is correct for you.

Insert Statements

Insert statements are the standard way of loading data into a database system. They are suitable for quick prototyping, but should be avoided for bulk loading as they have significant per-row overhead.

INSERT INTO people VALUES (1, 'Mark');

See here for a more detailed description of insert statements.

CSV Loading

Data can be efficiently loaded from CSV files using the read_csv_auto function or the COPY statement.

SELECT * FROM read_csv_auto('test.csv');

You can also load data from compressed (e.g. compressed with gzip) CSV files, for example:

SELECT * FROM read_csv_auto('test.csv.gz');

See here for a detailed description of CSV loading.

Parquet Loading

Parquet files can be efficiently loaded and queried using the read_parquet function.

SELECT * FROM read_parquet('test.parquet');

See here for a detailed description of Parquet loading.

JSON Loading

JSON files can be efficiently loaded and queried using the read_json_auto function.

SELECT * from read_json_auto('test.json');

See here for a detailed description of JSON loading.

Appender (C++ and Java)

In C++ and Java, the appender can be used as an alternative for bulk data loading. This class can be used to efficiently add rows to the database system without needing to use SQL.

C++:

Appender appender(con, "people");
appender.AppendRow(1, "Mark");
appender.Close();

Java:

con.createAppender("main", "people");
appender.beginRow();
appender.append("Mark");
appender.endRow();
appender.close();

See here for a detailed description of the C++ appender.