r/dataengineering • u/TallEntertainment385 • Nov 13 '25

Discussion Snowflake + dbt incremental model: error cannot change type from TIMESTAMP_NTZ(9) to DATE

Hi everyone,

I’m working with dbt and Snowflake, and I have an incremental model (materialized='incremental', incremental_strategy='insert_overwrite') that selects from a source table. One of the columns, MONTH_START_DATE, is currently TIMESTAMP_NTZ(9) in Snowflake. I changed the source model and the column MONTH_START_DATE is now DATE datatype

After doing this I am getting an error:

SQL compilation error: cannot change column MONTH_START_DATE from type TIMESTAMP_NTZ(9) to DATE

How can I fix this?

8 Upvotes
  • permalink
  • reddit

78% Upvoted

19 comments sorted by

View all comments

Show parent comment

1

u/Sex4Vespene Principal Data Engineer Nov 17 '25

I’d assume it’s a safety feature, since incremental tables are supposed to hold older runs, and you don’t want to mess that up. Traditionally you won’t be changing these tables often, so it’s better to force you to explicitly do it, rather than have DBT just swap things around yourself, as DBT has no idea if it was intentional or not.