The snippet library.
Small, practical examples. Search by task or narrow things down below.
Read a page after a known unique key
Postgres: A keyset predicate avoids scanning and discarding an increasing offset on a suitable index.
Postgres✓ Tested
Read named columns from a table
Postgres: Choose the columns needed and request a deterministic row order.
Postgres✓ Tested
Read the last value of the complete partition
Postgres: Specify an unbounded-following frame so LAST_VALUE does not stop at the current row.
Postgres✓ Tested
Read the next row’s value
Postgres: LEAD reads a later ordered row without a self join and supports a fallback at the end.
Postgres✓ Tested
Read the smallest and largest values
Postgres: Use MIN and MAX without sorting and fetching every row.
Postgres✓ Tested
Read updated base-table values through a view
Postgres: An ordinary view reflects later changes to its underlying data.
Postgres✓ Tested
Reference a parent identified by two columns
Postgres: A composite foreign key checks the complete referenced key rather than either column independently.
Postgres✓ Tested
Reject a negative quantity with CHECK
Postgres: Combine NOT NULL and CHECK because an unknown NULL check result is normally accepted.
Postgres✓ Tested
Reject duplicate business identifiers
Postgres: A UNIQUE constraint protects a business key independently of the primary key.
Postgres✓ Tested
Remove dependent rows with a declared cascade
Postgres: ON DELETE CASCADE removes children when their referenced parent is deleted.
Postgres✓ Tested
Remove duplicate result values
Postgres: Use DISTINCT when repeated category values are not useful.
Postgres✓ Tested
Remove duplicate values while keeping the smallest key
Postgres: Identify retained keys in a grouped subquery before deleting other copies.
Postgres✓ Tested