SQL tests fail in CI

[sambles]

Issue Description

Marked the following 4 checks as skipped, needs fixing f628100

FAILED tests/df_reader/test_sql.py::test_sql__validity[SELECT CONCAT(A, B) as "count_A" FROM table] - ValueError: Metadata inference failed in `add`.
FAILED tests/df_reader/test_sql.py::test_sql__result__joined - ValueError: You are trying to merge on object and datetime64[ns] columns for key 'common_0'. If you wish to proceed you should use pd.concat
FAILED tests/df_reader/test_sql.py::test_sql__result__joined__where - ValueError: You are trying to merge on object and datetime64[ns] columns for key 'common_0'. If you wish to proceed you should use pd.concat
FAILED tests/df_reader/test_sql.py::test_sql__result__joined__multi - ValueError: You are trying to merge on object and datetime64[ns] columns for key 'common_0'. If you wish to proceed you should use pd.concat

test-errors.txt