Yes definitely, we can do ETL testing without using any automation tool. For that, there are several steps we have to follow. For this, we can use Excel and SQL queries.

First step in which we can check source and target data. We write queries on the source and target tables, then compare the results.

In second step we check row count. Count rows in source and target to confirm they match.

In third step we check data values. Take sample data from source and target to ensure it matches.

In fourth step we check transformations. For transformed data, calculate in SQL/Excel and compare with target.

Then we have fifth step in which we check null and duplicate. We can run queries for nulls and duplicates to ensure data is correct.

And in last step we check incremental load. Add rows in source and check they reflect in target.