To export the data from a table to an Excel file, install and load the spatial extension, then use the COPY statement. The file will contain one worksheet with the same name as the file, but without the .xlsx extension.

INSTALL spatial; -- Only needed once per DuckDB connection
LOAD spatial; -- Only needed once per DuckDB connection

COPY tbl TO 'output.xlsx' WITH (FORMAT GDAL, DRIVER 'xlsx');

The result of queries can also be directly exported to an Excel file.

INSTALL spatial; -- Only needed once per DuckDB connection
LOAD spatial; -- Only needed once per DuckDB connection

COPY (SELECT * FROM tbl) TO 'output.xlsx' WITH (FORMAT GDAL, DRIVER 'xlsx');

Note: Dates and timestamps are not supported by the xlsx writer driver. Cast columns of those types to VARCHAR prior to creating the xlsx file.

Note: The output file must not already exist.

For additional details, see the spatial extension page and the GDAL XLSX driver page.