1 SELECT, WHERE & basic filtering Beginner Beginner – 1 2 3 4 5 2 DISTINCT and de-duplication Beginner Beginner – 1 2 3 4 5 3 ORDER BY multi-column sorting Beginner Beginner – 1 2 3 4 5 4 LIMIT / TOP / FETCH FIRST Beginner Beginner – 1 2 3 4 5 5 Aliases and column naming Beginner Beginner – 1 2 3 4 5 6 Comparison & logical operators Beginner Beginner – 1 2 3 4 5 7 IN, BETWEEN, LIKE patterns Beginner Beginner – 1 2 3 4 5 8 NULL handling with IS NULL / COALESCE Beginner Beginner – 1 2 3 4 5 9 CASE WHEN expressions Beginner Beginner – 1 2 3 4 5 10 String functions (CONCAT, SUBSTRING, TRIM) Beginner Beginner – 1 2 3 4 5 11 Date functions basics Beginner Beginner – 1 2 3 4 5 12 CAST and data type conversion Beginner Beginner – 1 2 3 4 5 13 Arithmetic & rounding Beginner Beginner – 1 2 3 4 5 14 Aggregate functions (SUM, AVG, MIN, MAX) Beginner Beginner – 1 2 3 4 5 15 COUNT vs COUNT(DISTINCT) Beginner Beginner – 1 2 3 4 5 16 GROUP BY fundamentals Beginner Beginner – 1 2 3 4 5 17 HAVING vs WHERE Beginner Beginner – 1 2 3 4 5 18 Conditional aggregation Intermediate Intermediate – 1 2 3 4 5 19 UNION vs UNION ALL Beginner Beginner – 1 2 3 4 5 20 EXCEPT / INTERSECT set operations Advanced Advanced – 1 2 3 4 5 21 INNER JOIN basics Beginner Beginner – 1 2 3 4 5 22 LEFT JOIN basics Beginner Beginner – 1 2 3 4 5 23 RIGHT JOIN & FULL OUTER JOIN Intermediate Intermediate – 1 2 3 4 5 24 Self Join patterns Intermediate Intermediate – 1 2 3 4 5 25 Cross Join & cartesian products Intermediate Intermediate – 1 2 3 4 5 26 Multi-table joins Intermediate Intermediate – 1 2 3 4 5 27 Semi-join with EXISTS Intermediate Intermediate – 1 2 3 4 5 28 Anti-join (NOT EXISTS / LEFT JOIN NULL) Intermediate Intermediate – 1 2 3 4 5 29 LATERAL / CROSS APPLY joins Advanced Advanced – 1 2 3 4 5 30 Subqueries in WHERE Intermediate Intermediate – 1 2 3 4 5 31 Subqueries in FROM (derived tables) Intermediate Intermediate – 1 2 3 4 5 32 Scalar subqueries Intermediate Intermediate – 1 2 3 4 5 33 Correlated subqueries Intermediate Intermediate – 1 2 3 4 5 34 Common Table Expressions (CTEs) Intermediate Intermediate – 1 2 3 4 5 35 Multiple chained CTEs Intermediate Intermediate – 1 2 3 4 5 36 PIVOT rows to columns Intermediate Intermediate – 1 2 3 4 5 37 UNPIVOT columns to rows Intermediate Intermediate – 1 2 3 4 5 38 Pivoting dynamic columns Advanced Advanced – 1 2 3 4 5 39 GROUPING SETS Intermediate Intermediate – 1 2 3 4 5 40 ROLLUP and CUBE Intermediate Intermediate – 1 2 3 4 5 41 Window function basics (OVER) Intermediate Intermediate – 1 2 3 4 5 42 PARTITION BY clause Intermediate Intermediate – 1 2 3 4 5 43 ROW_NUMBER() Intermediate Intermediate – 1 2 3 4 5 44 RANK() vs DENSE_RANK() Intermediate Intermediate – 1 2 3 4 5 45 NTILE() bucketing Intermediate Intermediate – 1 2 3 4 5 46 LAG() and LEAD() Intermediate Intermediate – 1 2 3 4 5 47 FIRST_VALUE / LAST_VALUE Intermediate Intermediate – 1 2 3 4 5 48 Running totals with SUM OVER Intermediate Intermediate – 1 2 3 4 5 49 Moving average with frame clause Intermediate Intermediate – 1 2 3 4 5 50 Conditional window frames Advanced Advanced – 1 2 3 4 5 51 Percent of total Intermediate Intermediate – 1 2 3 4 5 52 Cumulative distribution Intermediate Intermediate – 1 2 3 4 5 53 Median & percentile (PERCENTILE_CONT) Advanced Advanced – 1 2 3 4 5 54 Date truncation & bucketing Intermediate Intermediate – 1 2 3 4 5 55 Generate date series / calendar table Intermediate Intermediate – 1 2 3 4 5 56 Year-over-year growth Advanced Advanced – 1 2 3 4 5 57 Month-over-month change Advanced Advanced – 1 2 3 4 5 58 Rolling 7/30 day metrics Advanced Advanced – 1 2 3 4 5 59 Top-N per group Advanced Advanced – 1 2 3 4 5 60 Deduplicate keeping latest record Advanced Advanced – 1 2 3 4 5 61 Slowly changing dimension queries Advanced Advanced – 1 2 3 4 5 62 Recursive CTEs Advanced Advanced – 1 2 3 4 5 63 Hierarchical / org-chart queries Advanced Advanced – 1 2 3 4 5 64 Graph traversal in SQL Advanced Advanced – 1 2 3 4 5 65 Gaps and Islands problem Advanced Advanced – 1 2 3 4 5 66 Detecting consecutive streaks Advanced Advanced – 1 2 3 4 5 67 Sessionization of events Advanced Advanced – 1 2 3 4 5 68 Retention analysis Advanced Advanced – 1 2 3 4 5 69 Cohort analysis Advanced Advanced – 1 2 3 4 5 70 Funnel / conversion analysis Advanced Advanced – 1 2 3 4 5 71 First & last touch attribution Advanced Advanced – 1 2 3 4 5 72 Market basket / co-occurrence Advanced Advanced – 1 2 3 4 5 73 JSON parsing in SQL Advanced Advanced – 1 2 3 4 5 74 Array & nested data handling Advanced Advanced – 1 2 3 4 5 75 Regex matching in SQL Advanced Advanced – 1 2 3 4 5 76 Query optimization & cost reduction Expert Expert – 1 2 3 4 5 77 Reading EXPLAIN / execution plans Expert Expert – 1 2 3 4 5 78 Query rewriting for performance Expert Expert – 1 2 3 4 5 79 Avoiding full table scans Expert Expert – 1 2 3 4 5 80 Anti-pattern detection Expert Expert – 1 2 3 4 5 81 Index design (B-tree, composite) Expert Expert – 1 2 3 4 5 82 Covering indexes Expert Expert – 1 2 3 4 5 83 Index selectivity & cardinality Expert Expert – 1 2 3 4 5 84 Bitmap indexing Expert Expert – 1 2 3 4 5 85 Partitioning strategies Expert Expert – 1 2 3 4 5 86 Partition pruning Expert Expert – 1 2 3 4 5 87 Materialized views Expert Expert – 1 2 3 4 5 88 Columnar vs row storage Expert Expert – 1 2 3 4 5 89 Sharding & distributed SQL Expert Expert – 1 2 3 4 5 90 Join algorithms (hash, merge, nested loop) Expert Expert – 1 2 3 4 5 91 Statistics & the optimizer Expert Expert – 1 2 3 4 5 92 Cardinality estimation Expert Expert – 1 2 3 4 5 93 CTE materialization trade-offs Expert Expert – 1 2 3 4 5 94 Spilling & memory management Expert Expert – 1 2 3 4 5 95 Window function performance tuning Expert Expert – 1 2 3 4 5 96 Handling skew in aggregations Expert Expert – 1 2 3 4 5 97 Approximate distinct (HLL) Expert Expert – 1 2 3 4 5 98 Isolation levels (ACID) Expert Expert – 1 2 3 4 5 99 Deadlocks & locking Expert Expert – 1 2 3 4 5 100 MVCC concepts Expert Expert – 1 2 3 4 5 101 Recursive CTEs → Daily Active Users Advanced Advanced – 1 2 3 4 5 102 Query optimization & cost reduction → Monthly Revenue Expert Expert – 1 2 3 4 5 103 RIGHT JOIN & FULL OUTER JOIN → Customer Lifetime Value Intermediate Intermediate – 1 2 3 4 5 104 Hierarchical / org-chart queries → Churn Rate Advanced Advanced – 1 2 3 4 5 105 Reading EXPLAIN / execution plans → Average Order Value Expert Expert – 1 2 3 4 5 106 Self Join patterns → Conversion Funnel Intermediate Intermediate – 1 2 3 4 5 107 Graph traversal in SQL → New vs Returning Customers Advanced Advanced – 1 2 3 4 5 108 Index design (B-tree, composite) → Top Selling Products Expert Expert – 1 2 3 4 5 109 Cross Join & cartesian products → Inventory Turnover Intermediate Intermediate – 1 2 3 4 5 110 Gaps and Islands problem → Employee Hierarchy Advanced Advanced – 1 2 3 4 5 111 Covering indexes → Fraud Pattern Detection Expert Expert – 1 2 3 4 5 112 Multi-table joins → Session Duration Intermediate Intermediate – 1 2 3 4 5 113 Sessionization of events → A/B Test Results Advanced Advanced – 1 2 3 4 5 114 Index selectivity & cardinality → Subscription Renewals Expert Expert – 1 2 3 4 5 115 Anti-join (NOT EXISTS / LEFT JOIN NULL) → Refund Analysis Intermediate Intermediate – 1 2 3 4 5 116 Retention analysis → Lead Scoring Advanced Advanced – 1 2 3 4 5 117 Partitioning strategies → Page View Paths Expert Expert – 1 2 3 4 5 118 Semi-join with EXISTS → Cart Abandonment Intermediate Intermediate – 1 2 3 4 5 119 Cohort analysis → Loyalty Tiers Advanced Advanced – 1 2 3 4 5 120 Partition pruning → Regional Sales Split Expert Expert – 1 2 3 4 5 121 Subqueries in WHERE → Daily Active Users Intermediate Intermediate – 1 2 3 4 5 122 Funnel / conversion analysis → Monthly Revenue Advanced Advanced – 1 2 3 4 5 123 Materialized views → Customer Lifetime Value Expert Expert – 1 2 3 4 5 124 Subqueries in FROM (derived tables) → Churn Rate Intermediate Intermediate – 1 2 3 4 5 125 Median & percentile (PERCENTILE_CONT) → Average Order Value Advanced Advanced – 1 2 3 4 5 126 Query rewriting for performance → Conversion Funnel Expert Expert – 1 2 3 4 5 127 Scalar subqueries → New vs Returning Customers Intermediate Intermediate – 1 2 3 4 5 128 Top-N per group → Top Selling Products Advanced Advanced – 1 2 3 4 5 129 Avoiding full table scans → Inventory Turnover Expert Expert – 1 2 3 4 5 130 Correlated subqueries → Employee Hierarchy Intermediate Intermediate – 1 2 3 4 5 131 Deduplicate keeping latest record → Fraud Pattern Detection Advanced Advanced – 1 2 3 4 5 132 Join algorithms (hash, merge, nested loop) → Session Duration Expert Expert – 1 2 3 4 5 133 Common Table Expressions (CTEs) → A/B Test Results Intermediate Intermediate – 1 2 3 4 5 134 Year-over-year growth → Subscription Renewals Advanced Advanced – 1 2 3 4 5 135 Statistics & the optimizer → Refund Analysis Expert Expert – 1 2 3 4 5 136 Multiple chained CTEs → Lead Scoring Intermediate Intermediate – 1 2 3 4 5 137 Month-over-month change → Page View Paths Advanced Advanced – 1 2 3 4 5 138 Deadlocks & locking → Cart Abandonment Expert Expert – 1 2 3 4 5 139 Conditional aggregation → Loyalty Tiers Intermediate Intermediate – 1 2 3 4 5 140 Rolling 7/30 day metrics → Regional Sales Split Advanced Advanced – 1 2 3 4 5 141 Isolation levels (ACID) → Daily Active Users Expert Expert – 1 2 3 4 5 142 PIVOT rows to columns → Monthly Revenue Intermediate Intermediate – 1 2 3 4 5 143 First & last touch attribution → Customer Lifetime Value Advanced Advanced – 1 2 3 4 5 144 MVCC concepts → Churn Rate Expert Expert – 1 2 3 4 5 145 UNPIVOT columns to rows → Average Order Value Intermediate Intermediate – 1 2 3 4 5 146 Market basket / co-occurrence → Conversion Funnel Advanced Advanced – 1 2 3 4 5 147 Window function performance tuning → New vs Returning Customers Expert Expert – 1 2 3 4 5 148 GROUPING SETS → Top Selling Products Intermediate Intermediate – 1 2 3 4 5 149 Slowly changing dimension queries → Inventory Turnover Advanced Advanced – 1 2 3 4 5 150 Handling skew in aggregations → Employee Hierarchy Expert Expert – 1 2 3 4 5 151 ROLLUP and CUBE → Fraud Pattern Detection Intermediate Intermediate – 1 2 3 4 5 152 Detecting consecutive streaks → Session Duration Advanced Advanced – 1 2 3 4 5 153 Approximate distinct (HLL) → A/B Test Results Expert Expert – 1 2 3 4 5 154 Window function basics (OVER) → Subscription Renewals Intermediate Intermediate – 1 2 3 4 5 155 Pivoting dynamic columns → Refund Analysis Advanced Advanced – 1 2 3 4 5 156 Bitmap indexing → Lead Scoring Expert Expert – 1 2 3 4 5 157 PARTITION BY clause → Page View Paths Intermediate Intermediate – 1 2 3 4 5 158 Conditional window frames → Cart Abandonment Advanced Advanced – 1 2 3 4 5 159 Columnar vs row storage → Loyalty Tiers Expert Expert – 1 2 3 4 5 160 ROW_NUMBER() → Regional Sales Split Intermediate Intermediate – 1 2 3 4 5 161 EXCEPT / INTERSECT set operations → Daily Active Users Advanced Advanced – 1 2 3 4 5 162 Sharding & distributed SQL → Monthly Revenue Expert Expert – 1 2 3 4 5 163 RANK() vs DENSE_RANK() → Customer Lifetime Value Intermediate Intermediate – 1 2 3 4 5 164 LATERAL / CROSS APPLY joins → Churn Rate Advanced Advanced – 1 2 3 4 5 165 CTE materialization trade-offs → Average Order Value Expert Expert – 1 2 3 4 5 166 NTILE() bucketing → Conversion Funnel Intermediate Intermediate – 1 2 3 4 5 167 JSON parsing in SQL → New vs Returning Customers Advanced Advanced – 1 2 3 4 5 168 Spilling & memory management → Top Selling Products Expert Expert – 1 2 3 4 5 169 LAG() and LEAD() → Inventory Turnover Intermediate Intermediate – 1 2 3 4 5 170 Array & nested data handling → Employee Hierarchy Advanced Advanced – 1 2 3 4 5 171 Anti-pattern detection → Fraud Pattern Detection Expert Expert – 1 2 3 4 5 172 FIRST_VALUE / LAST_VALUE → Session Duration Intermediate Intermediate – 1 2 3 4 5 173 Regex matching in SQL → A/B Test Results Advanced Advanced – 1 2 3 4 5 174 Cardinality estimation → Subscription Renewals Expert Expert – 1 2 3 4 5 175 Running totals with SUM OVER → Refund Analysis Intermediate Intermediate – 1 2 3 4 5 176 Recursive CTEs → Lead Scoring Advanced Advanced – 1 2 3 4 5 177 Query optimization & cost reduction → Page View Paths Expert Expert – 1 2 3 4 5 178 Moving average with frame clause → Cart Abandonment Intermediate Intermediate – 1 2 3 4 5 179 Hierarchical / org-chart queries → Loyalty Tiers Advanced Advanced – 1 2 3 4 5 180 Reading EXPLAIN / execution plans → Regional Sales Split Expert Expert – 1 2 3 4 5 181 Percent of total → Daily Active Users Intermediate Intermediate – 1 2 3 4 5 182 Graph traversal in SQL → Monthly Revenue Advanced Advanced – 1 2 3 4 5 183 Index design (B-tree, composite) → Customer Lifetime Value Expert Expert – 1 2 3 4 5 184 Cumulative distribution → Churn Rate Intermediate Intermediate – 1 2 3 4 5 185 Gaps and Islands problem → Average Order Value Advanced Advanced – 1 2 3 4 5 186 Covering indexes → Conversion Funnel Expert Expert – 1 2 3 4 5 187 Date truncation & bucketing → New vs Returning Customers Intermediate Intermediate – 1 2 3 4 5 188 Sessionization of events → Top Selling Products Advanced Advanced – 1 2 3 4 5 189 Index selectivity & cardinality → Inventory Turnover Expert Expert – 1 2 3 4 5 190 Generate date series / calendar table → Employee Hierarchy Intermediate Intermediate – 1 2 3 4 5 191 Retention analysis → Fraud Pattern Detection Advanced Advanced – 1 2 3 4 5 192 Partitioning strategies → Session Duration Expert Expert – 1 2 3 4 5 193 RIGHT JOIN & FULL OUTER JOIN → A/B Test Results Intermediate Intermediate – 1 2 3 4 5 194 Cohort analysis → Subscription Renewals Advanced Advanced – 1 2 3 4 5 195 Partition pruning → Refund Analysis Expert Expert – 1 2 3 4 5 196 Self Join patterns → Lead Scoring Intermediate Intermediate – 1 2 3 4 5 197 Funnel / conversion analysis → Page View Paths Advanced Advanced – 1 2 3 4 5 198 Materialized views → Cart Abandonment Expert Expert – 1 2 3 4 5 199 Cross Join & cartesian products → Loyalty Tiers Intermediate Intermediate – 1 2 3 4 5 200 Median & percentile (PERCENTILE_CONT) → Regional Sales Split Advanced Advanced – 1 2 3 4 5 201 Query rewriting for performance → Daily Active Users Expert Expert – 1 2 3 4 5 202 Multi-table joins → Monthly Revenue Intermediate Intermediate – 1 2 3 4 5 203 Top-N per group → Customer Lifetime Value Advanced Advanced – 1 2 3 4 5 204 Avoiding full table scans → Churn Rate Expert Expert – 1 2 3 4 5 205 Anti-join (NOT EXISTS / LEFT JOIN NULL) → Average Order Value Intermediate Intermediate – 1 2 3 4 5 206 Deduplicate keeping latest record → Conversion Funnel Advanced Advanced – 1 2 3 4 5 207 Join algorithms (hash, merge, nested loop) → New vs Returning Customers Expert Expert – 1 2 3 4 5 208 Semi-join with EXISTS → Top Selling Products Intermediate Intermediate – 1 2 3 4 5 209 Year-over-year growth → Inventory Turnover Advanced Advanced – 1 2 3 4 5 210 Statistics & the optimizer → Employee Hierarchy Expert Expert – 1 2 3 4 5 211 Subqueries in WHERE → Fraud Pattern Detection Intermediate Intermediate – 1 2 3 4 5 212 Month-over-month change → Session Duration Advanced Advanced – 1 2 3 4 5 213 Deadlocks & locking → A/B Test Results Expert Expert – 1 2 3 4 5 214 Subqueries in FROM (derived tables) → Subscription Renewals Intermediate Intermediate – 1 2 3 4 5 215 Rolling 7/30 day metrics → Refund Analysis Advanced Advanced – 1 2 3 4 5 216 Isolation levels (ACID) → Lead Scoring Expert Expert – 1 2 3 4 5 217 Scalar subqueries → Page View Paths Intermediate Intermediate – 1 2 3 4 5 218 First & last touch attribution → Cart Abandonment Advanced Advanced – 1 2 3 4 5 219 MVCC concepts → Loyalty Tiers Expert Expert – 1 2 3 4 5 220 Correlated subqueries → Regional Sales Split Intermediate Intermediate – 1 2 3 4 5 221 Market basket / co-occurrence → Daily Active Users Advanced Advanced – 1 2 3 4 5 222 Window function performance tuning → Monthly Revenue Expert Expert – 1 2 3 4 5 223 Common Table Expressions (CTEs) → Customer Lifetime Value Intermediate Intermediate – 1 2 3 4 5 224 Slowly changing dimension queries → Churn Rate Advanced Advanced – 1 2 3 4 5 225 Handling skew in aggregations → Average Order Value Expert Expert – 1 2 3 4 5 226 Multiple chained CTEs → Conversion Funnel Intermediate Intermediate – 1 2 3 4 5 227 Detecting consecutive streaks → New vs Returning Customers Advanced Advanced – 1 2 3 4 5 228 Approximate distinct (HLL) → Top Selling Products Expert Expert – 1 2 3 4 5 229 Conditional aggregation → Inventory Turnover Intermediate Intermediate – 1 2 3 4 5 230 Pivoting dynamic columns → Employee Hierarchy Advanced Advanced – 1 2 3 4 5 231 Bitmap indexing → Fraud Pattern Detection Expert Expert – 1 2 3 4 5 232 PIVOT rows to columns → Session Duration Intermediate Intermediate – 1 2 3 4 5 233 Conditional window frames → A/B Test Results Advanced Advanced – 1 2 3 4 5 234 Columnar vs row storage → Subscription Renewals Expert Expert – 1 2 3 4 5 235 UNPIVOT columns to rows → Refund Analysis Intermediate Intermediate – 1 2 3 4 5 236 EXCEPT / INTERSECT set operations → Lead Scoring Advanced Advanced – 1 2 3 4 5 237 Sharding & distributed SQL → Page View Paths Expert Expert – 1 2 3 4 5 238 GROUPING SETS → Cart Abandonment Intermediate Intermediate – 1 2 3 4 5 239 LATERAL / CROSS APPLY joins → Loyalty Tiers Advanced Advanced – 1 2 3 4 5 240 CTE materialization trade-offs → Regional Sales Split Expert Expert – 1 2 3 4 5 241 ROLLUP and CUBE → Daily Active Users Intermediate Intermediate – 1 2 3 4 5 242 JSON parsing in SQL → Monthly Revenue Advanced Advanced – 1 2 3 4 5 243 Spilling & memory management → Customer Lifetime Value Expert Expert – 1 2 3 4 5 244 Window function basics (OVER) → Churn Rate Intermediate Intermediate – 1 2 3 4 5 245 Array & nested data handling → Average Order Value Advanced Advanced – 1 2 3 4 5 246 Anti-pattern detection → Conversion Funnel Expert Expert – 1 2 3 4 5 247 PARTITION BY clause → New vs Returning Customers Intermediate Intermediate – 1 2 3 4 5 248 Regex matching in SQL → Top Selling Products Advanced Advanced – 1 2 3 4 5 249 Cardinality estimation → Inventory Turnover Expert Expert – 1 2 3 4 5 250 ROW_NUMBER() → Employee Hierarchy Intermediate Intermediate – 1 2 3 4 5 251 Recursive CTEs → Fraud Pattern Detection Advanced Advanced – 1 2 3 4 5 252 Query optimization & cost reduction → Session Duration Expert Expert – 1 2 3 4 5 
