sqlcmd.net validated sql reference

Tag archive

#duplicates

Commands grouped around the same concept, pattern, or recurring problem.

3 commands with this tag Browse related patterns quickly
intermediate filtering MySQL MariaDB SQL Server PostgreSQL SQLite

Avoid Duplicate Parent Rows With EXISTS

Use `EXISTS` when you only need to test whether a related row exists, not return one output row per match.

intermediate set-operations MySQL MariaDB SQL Server PostgreSQL SQLite

Choose UNION Or UNION ALL Intentionally

`UNION` removes duplicates, while `UNION ALL` keeps them. Picking the wrong one silently changes row counts.

intermediate data-quality MySQL MariaDB SQL Server PostgreSQL SQLite

Find Duplicate Values With GROUP BY And HAVING

Group rows by the candidate key and keep only values that appear more than once.