@zz_knime welcome to the KNIME forum
two things. In the DB node you should be able to set a type mapping. Then there is the option to use a CAST statement to force the desired format like
CAST(my_var AS DOUBLE) AS my_new_var_double
CAST(my_var AS BIGINT) AS my_new_var_bigint
This is also useful to do if sometimes your data sources would contain unwanted elements and your DB would then reject your input data.
For example you could set types in the DB Table Creator node:
Or the SQLite connector:
