I set google analytics as a data source and my query result was a table, then I wanted to use this query as a source table and query on this table. the problem is I want to convert date from day to week and I used the date_trunc function but announced error " Error running the query: no such function: date_trunc"
what function can I use instead date_trunc?

The Query Results data source uses SQLite, so you need to use SQLite date functions: https://www.sqlite.org/lang_datefunc.html.