Spark SQL is different from KSQL in the following ways:

- Spark SQL is not an interactive Streaming SQL interface. To do stream processing, you have to switch between writing code using Java/Scala/Python and SQL statements. KSQL, on the other hand, is a completely interactive Streaming SQL engine. You can do sophisticated stream processing operations interactively using SQL statements alone.

- KSQL is a true event-at-a-time Streaming SQL engine. Spark SQL is micro-batch.

What you said about Spark was not true. One can totally interactively query a Kafka stream using Spark, in SQL.