SQL Practical Guides
Use focused guides when you know the job you need to do and want a verified pattern, a realistic example and the next tool or practice step.
SQL LIKE Multiple Values
Match several text patterns without losing readability.
Open →SQLSQL LIKE Starts With
Filter codes by a known prefix.
Open →SQLSQL LIKE Contains Text
Find rows where a code or description contains a fragment.
Open →SQLSQL NOT LIKE
Exclude rows that match a text pattern.
Open →SQLSQL LEFT JOIN to Find Missing Rows
Keep every source row and expose records with no match.
Open →SQLSQL JOIN Creates Duplicate Rows
Understand why a JOIN returns more rows than expected.
Open →SQLSQL GROUP BY Multiple Columns
Summarize data at the exact business grain you need.
Open →SQLSQL WHERE vs HAVING
Choose the correct filter stage before or after aggregation.
Open →SQLSQL CASE with Multiple Conditions
Turn business rules into readable status labels.
Open →SQLCTE vs Subquery
Choose between a named intermediate result and an inline nested query.
Open →SQLRemove SQL Duplicates with ROW_NUMBER
Keep one row from each duplicate group using an explicit rule.
Open →SQLSQL Top N Per Group
Return the highest or latest rows inside each business group.
Open →SQLSQL Running Total
Calculate cumulative values in a defined order.
Open →SQLSQL LAG and LEAD
Compare a row with the previous or next event.
Open →SQLSQL NULL Handling
Work safely with missing or unknown values.
Open →SQLSQL EXISTS vs IN
Choose a clear membership test for related data.
Open →SQLSQL UNION vs UNION ALL
Append result sets with or without duplicate removal.
Open →SQLSQL Last 30 Days Filter
Build rolling date filters that update automatically.
Open →SQLSQL Find Duplicate Values
Identify keys that occur more often than expected.
Open →SQLSQL Query Performance Basics
Make operational queries easier for the optimizer without premature tuning.
Open →SQLSQL Conditional Aggregation
Build several KPI counts in one grouped query.
Open →SQLSQL Pivot with CASE
Turn categories into summary columns without vendor-specific PIVOT syntax.
Open →SQLSQL Anti Join Patterns
Find records that exist in one set but not another.
Open →SQLSQL Latest Row Per Key
Return the newest status or event for each item.
Open →SQLSafe SQL UPDATE Workflow
Preview exactly what an UPDATE will touch before changing data.
Open →