The snippet library.
Small, practical examples. Search by task or narrow things down below.
Count rows satisfying separate conditions
Postgres: SUM over CASE expressions calculates several conditional counts in one scan.
Postgres✓ Tested
Count the rows in a table
Postgres: COUNT(*) includes every row, including rows with NULL columns.
Postgres✓ Tested
Create a table and insert its first row
Postgres: Define column types and a primary key, then insert one row using an explicit column list.
Postgres✓ Tested
Create an index for an equality filter
Postgres: A nonunique index can support lookups on a frequently filtered column.
Postgres✓ Tested
Create an index matching filter and ordering columns
Postgres: Place the equality-filter column before the ordering column in this composite index.
Postgres✓ Tested
Delete one row from a practice table
Postgres: Restrict DELETE with a primary-key condition and verify the remaining row count.
Postgres✓ Tested
Delete rows selected by a related table
Postgres: A correlated EXISTS limits the delete to explicitly listed records.
Postgres✓ Tested
Display a fallback for missing data
Postgres: Return a supplied label when a column contains NULL.
Postgres✓ Tested
Distinguish row count from non-null value count
Postgres: COUNT(*) includes every row while COUNT(column) skips NULL values.
Postgres✓ Tested
Divide an ordered result into numbered buckets
Postgres: NTILE distributes rows across buckets; include a unique tie-breaker for deterministic assignment.
Postgres✓ Tested
Enforce a bounded numeric range
Postgres: A named CHECK constraint keeps numeric values inside an inclusive interval.
Postgres✓ Tested
Enforce a relationship between two columns
Postgres: A row-level CHECK can require a start value to be no greater than an end value.
Postgres✓ Tested