The snippet library.
Small, practical examples. Search by task or narrow things down below.
Join a parent to pre-aggregated totals
SQL: Aggregate the child rows first to produce at most one joined row per parent.
SQL✓ Tested
Join related rows from two tables
SQL: Match a category key to its display label with an explicit join condition.
SQL✓ Tested
Join through a lookup table
SQL: Use explicit aliases and join keys when enriching records through two relationships.
SQL✓ Tested
Keep children while clearing a deleted relationship
SQL: ON DELETE SET NULL requires a nullable foreign-key column.
SQL✓ Tested
Keep parent rows while filtering joined children
SQL: Put a child filter in ON when unmatched parents must remain in the result.
SQL✓ Tested
Keep rows matching a condition
SQL: Use WHERE to select rows with a particular category.
SQL✓ Tested
Keep unmatched rows with LEFT JOIN
Show every product even when stock is missing.
LEFT JOIN✓ Tested
Label rows with CASE
Derive a readable label from a condition.
CASE✓ Tested
List distinct values
Remove duplicate category values from a result.
DISTINCT✓ Tested
List unordered pairs without duplicate reversals
SQL: Join using an increasing key comparison to omit self-pairs and reversed duplicates.
SQL✓ Tested
Make a pair of columns unique together
SQL: A composite primary key permits repeated individual values while forbidding a duplicate combination.
SQL✓ Tested
Match a known text prefix
SQL: A percent wildcard matches zero or more characters following the prefix.
SQL✓ Tested