In this case. A query that you build by adding different strings. 1=1 is for adding AND statements to the WHERE clause dynamically. In your code. I never seen it used for anything else. Adhoc is just the practice of running raw SQL queries.

So you end up with things like this.

"SELECT * FROM Music WHERE 1=1" + "AND category='rock'"

The risk is now that you by mistake allow for SQL-injections but also every genre will generate a different query plan. Depending on what SQL engine you use this may hurt performance.

And one would think that this is a thing of the past. But it is not.