I need to investigate data quality issues systematically. Let me examine the evidence I have and then probe for specific quality problems. From the evidence so far, I can see several issues already: 1. **Rank=0 with Points>0**: 14,661 rows in ittf_rankings and 11,224 in ittf_rankings_women have Rank=0 but non-zero Points 2. **Gender mismatches**: ittf_rankings has 6 'W' records and 14 blank Gender values; ittf_rankings_women has 21 'M' records and 1 blank 3. **Duplicate ranks**: 47,662 instances in ittf_rankings and 30,885 in ittf_rankings_women where the same rank appears multiple times in a period 4. **Missing months**: Several year-month combinations are absent (2002-12, 2005-3, 2006-1, all of 2009, 2019-2020) 5. **MonthNum=0**: In 2019-2020, MonthNum is 0 instead of 1-12 Let me check for additional quality issues around the Previous/Previous Points relationship and temporal consistency: ```json { "action": "tool_call", "reasoning": "Need to check the relationship between Previous and Previous Points columns - they should be consistent (if Previous rank exists, Previous Points should exist too). Also want to verify if there are cases where Previous Points changed but Previous rank didn't, or vice versa.", "tool": "query_sql", "args": { "sql": "SELECT 'ittf_rankings' as table_name, COUNT(CASE WHEN Previous IS NOT NULL AND \"Previous Points\" IS NULL THEN 1 END) as prev_rank_no_prev_points, COUNT(CASE WHEN Previous IS NULL AND \"Previous Points\" IS NOT NULL THEN 1 END) as prev_points_no_prev_rank, COUNT(CASE WHEN Previous IS NOT NULL AND \"Previous Points\" IS NOT NULL AND Previous = Rank AND \"Previous Points\" != Points THEN 1 END) as same_rank_diff_points, COUNT(CASE WHEN Previous IS NOT NULL AND \"Previous Points\" IS NOT NULL AND Previous != Rank AND \"Previous Points\" = Points THEN 1 END) as diff_rank_same_points FROM raw.ittf_rankings UNION ALL SELECT 'ittf_rankings_women', COUNT(CASE WHEN Previous IS NOT NULL AND \"Previous Points\" IS NULL THEN 1 END), COUNT(CASE WHEN Previous IS NULL AND \"Previous Points\" IS NOT NULL THEN 1 END), COUNT(CASE WHEN Previous IS NOT NULL AND \"Previous Points\" IS NOT NULL AND Previous = Rank AND \"Previous Points\" != Points THEN 1 END), COUNT(CASE WHEN Previous IS NOT NULL AND \"Previous Points\" IS NOT NULL AND Previous != Rank AND \"Previous Points\" = Points THEN 1 END) FROM raw.ittf_rankings_women", "purpose": "Check consistency between Previous rank and Previous Points columns" } } ```