# Glossary One row per term in the [SQL Database](/en/documentation/platform/sql-database/) documentation, with the page that owns the term linked from its definition. | Term | Definition | | -------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `azion/sql` | The export of the [`azion` library](/en/documentation/devtools/azion-lib/sql/) that creates databases and runs queries from Node or TypeScript. It carries `createDatabase`, `getDatabase`, `getDatabases`, `deleteDatabase`, `useQuery`, `useExecute`, and `getTables`. Its fields are camelCased, and a query through it drops `rows_read`, `rows_written`, and `query_duration_ms`. | | `azion:sql` | The [Azion Runtime](/en/documentation/devtools/runtime/api-reference/sql-database/) module a function imports to run SQL during the request it handles. The import is `import { Database } from "azion:sql"`. | | `AZION_TOKEN` | The environment variable that holds the [personal token](/en/documentation/guides/platform/account-and-billing/personal-tokens/) the [EdgeSQL Shell](/en/documentation/platform/sql-database/edgesql-shell/) and the `azion` library authenticate with. Both read the value from the environment rather than from an argument. | | database | The object SQL Database creates, and the unit a query runs against. A name holds 6 to 50 characters, accepts letters, numbers, and the hyphen, and is unique within the account. A database cannot be renamed after creation, and [Databases and queries](/en/documentation/platform/sql-database/databases-and-queries/) documents every field it carries. | | EdgeSQL Shell | The Python command-line tool that creates databases, runs SQL, and imports data from a terminal. Its prompt is `EdgeSQL>`, and it is installed from source rather than from a package index. [EdgeSQL Shell](/en/documentation/platform/sql-database/edgesql-shell/) documents every command, option, and environment variable. | | main instance | The instance of a database that takes the writes. Azion replicates it to the read replicas that answer the reads, as [How it works](/en/documentation/platform/sql-database/how-it-works/) describes. | | Preview | The release stage SQL Database carries on every plan. A Preview product is not enabled on an account by default, and access is requested from the [technical support team](/en/documentation/support/). | | read replica | A copy of a database that answers the statements that only read. The write target is the main instance, and [How it works](/en/documentation/platform/sql-database/how-it-works/) describes how a query reaches the data. | | rows read | The number of rows one statement read, returned as `rows_read` beside the result of that statement. Azion meters it, and [SQL Database limits](/en/documentation/platform/sql-database/limits/) carries the amount each plan includes. | | rows written | The number of rows one statement wrote, returned as `rows_written` beside the result of that statement. It is the second metered value, and [SQL Database limits](/en/documentation/platform/sql-database/limits/) carries the daily amount each plan includes. | | SQL Database | The Azion product that stores [relational data](https://www.azion.com/en/learning/storage-database/what-is-relational-database/) and runs SQL against it, in the [SQLite dialect](https://www.sqlite.org/lang.html). It is a Store product, alongside [Object Storage](/en/documentation/platform/object-storage/) and [KV Store](/en/documentation/platform/kv-store/). You reach it from Azion Console, the Azion API, the `azion` library, Azion Runtime, and the EdgeSQL Shell. | | statement | One SQL string in the `statements` array of a query request. Each statement returns its own entry in `data`, in the order it was sent. A statement that fails carries `error` in place of `results`, inside an HTTP `200` response, as [Databases and queries](/en/documentation/platform/sql-database/databases-and-queries/) documents. | | status | The provisioning state of a database: `creating`, `created`, or `deleting`. It is not the `state` key of the response envelope, which reads `pending` on the answer to a create or a delete. [Databases and queries](/en/documentation/platform/sql-database/databases-and-queries/) documents both. | | vector column | A column that holds a vector, such as an [embedding](https://www.azion.com/en/learning/ai/what-are-embeddings-and-vectors/), declared with a type that states the dimension count. The types are `FLOAT1BIT`, `FLOAT8`, `FLOATB16`, `FLOAT16`, `FLOAT32`, and `FLOAT64`, each with a blob alias such as `F32_BLOB(3)`. [Vector search](/en/documentation/platform/sql-database/vector-search/) documents the types and the functions that read them. | | vector index | The approximate-nearest-neighbor index a column receives when `CREATE INDEX` wraps it in `libsql_vector_idx`. It is supported on a table with a `ROWID` or a single-column `PRIMARY KEY`, and it adds a shadow table named `_shadow`. [Vector search](/en/documentation/platform/sql-database/vector-search/) documents the index and the DiskANN algorithm behind it. | | `vector_top_k` | The function that returns the `k` rows nearest to a vector, as `id` values read from a named vector index. A query joins that result on `rowid` to read the rows themselves. [Vector search](/en/documentation/platform/sql-database/vector-search/) shows the full statement. |