This mock exam follows the shape of the SQL parts of cloud data warehouse certifications such as SnowPro Core: multiple-choice questions on how SQL behaves, mixed with short queries. The questions are written for this site; they aren't taken from any real exam.
Give yourself 30 minutes and work straight through. Questions you can answer by reasoning are faster than the ones you write, so do those first and come back. Where a question names a function that differs by database, the answer uses the standard or Snowflake-style form, which the database here also accepts.