ANSI Compatibility

GreptimeDB supports a subset of ANSI SQL and has some unique extensions. Some major incompatibilities and extensions are described below:

1. Create a table:
   • Supports the unique TIME INDEX constraint. Please refer to the Data Model and the CREATE table creation syntax for details.
   • Currently only supports PRIMARY KEY constraints and does not support other types of constraints or foreign keys.
   • GreptimeDB is a native distributed database, so the table creation syntax for distributed tables supports partitioning rules. Please also refer to the CREATE.
2. Insert data: Consistent with ANSI SQL syntax, but requires the TIME INDEX column value (or default value) to be provided.
3. Update data: Does not support UPDATE syntax, but if the primary key and TIME INDEX corresponding column values are the same during INSERT, subsequent inserted rows will overwrite previously written rows, effectively achieving an update.
   • Since 0.8, GreptimeDB supports append mode that creates an append-only table with append_mode="true" option which keeps duplicate rows.
4. Query data: Query syntax is compatible with ANSI SQL, with some functional differences and omissions.
   • Does not support views.
   • TQL syntax extension: Supports executing PromQL in SQL via TQL subcommands. Please refer to the TQL section for details.
   • Range Query to query and aggregate data within a range of time.
5. Delete data: Deletion syntax is basically consistent with ANSI SQL.
6. Others:
   • Identifiers such as table names and column names have constraints similar to ANSI SQL, are case sensitive, and require double quotes when encountering special characters or uppercase letters.
   • GreptimeDB has optimized identifier rules for different dialects. For example, when you connect with a MySQL or PostgreSQL client, you can use identifier rules specific to that SQL dialect, such as using backticks ` for MySQL and standard double quotes " for PostgreSQL.