Database cheatsheet

Elasticsearch 9 Cheatsheet

curl requests for indexes, documents, searches, bulk loads and cluster health. Security is on by default, so the examples authenticate.

Cluster and health

Check that the cluster is up — Return the cluster name and Elasticsearch version. Set ELASTIC_PASSWORD first, and point --cacert at your cluster's CA certificate.
Check cluster health — Show the status: green, yellow or red.
List nodes — Show nodes with their roles, load and memory.
List indices — Show indices with health, document counts and size.
List shards — Show where every shard is allocated.
Explain unassigned shards — Ask why a shard is not allocated.

Create an index — Create an index with explicit settings.
Define field types — Add a mapping so fields are analyzed the way you want.
Read a mapping — Show the field types of an index.
Add an alias — Point an alias at an index, so applications don't depend on the index name.
Copy documents to a new index — Copy documents from one index to another, for example after changing a mapping.
Delete an index — Delete an index and all its documents.

Index a document with an ID — Create or replace a document.
Index a document with a generated ID — Let Elasticsearch choose the ID.
Get a document — Fetch a single document by its ID.
Update fields — Merge fields into an existing document.
Delete a document — Delete a single document by its ID.
Load many documents — Index many documents from a newline-delimited JSON file. Each action line is followed by its document, and the file ends with a newline.
Count documents — Count the documents in an index.

Return everything — Return the first 10 documents.
Full-text search — Find documents whose name matches the text, ranked by relevance.
Exact match on a keyword — Match a keyword field exactly.
Combine conditions — Require a text match and filter by price without affecting the score.
Sort and paginate — Return 5 results starting at the tenth, cheapest first.
Aggregate — Compute the average price without returning documents.
See how text is analyzed — Show the tokens the standard analyzer produces.

DuckDB 2 cheatsheet — Query CSV, Parquet and DataFrames with SQL from Python or the duckdb command line, without running a server.
MongoDB 8 cheatsheet — mongosh shell commands for documents, queries, aggregation, indexes, backups and administration.
MySQL 8.4 cheatsheet — mysql client, backup and maintenance commands for MySQL 8.4.
PostgreSQL 18 cheatsheet — psql, backup and maintenance commands for PostgreSQL 18.
Redis 8 cheatsheet — redis-cli and core commands for keys, data structures and server administration.
SQLite 3 cheatsheet — sqlite3 shell dot-commands, pragmas, import and export, and the SQL you use most.