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Inspecting existing schemas with Atlas

Automatic Schema Inspection

Many projects begin with an existing database that users wish to start managing with Atlas. In this case, instead of having developers learn the Atlas Language and reverse engineer a schema definition file that precisely describes the existing database, Atlas supports automatic schema inspection.

With automatic schema inspection, users simply provide Atlas with a connection string to their target database and Atlas prints out a schema definition file in the Atlas language that they can use as the starting point for working with this database.

Flags

When using schema inspect to inspect an existing database, users may supply multiple parameters:

  • --url (-u accepted as well) - the URL of database to be inspected.
  • --schema (optional, may be supplied multiple times) - schemas to inspect within the target database.
  • --exclude (optional) - filter out resources matching the given glob pattern.
  • --format (optional) - Go template to use to format the output.

Examples

Inspect a database

The following commands demonstrate how to inspect the entire database, including all its schemas:

atlas schema inspect -u "mysql://localhost"

atlas schema inspect -u "mysql://user:pass@localhost:3306"

Inspect a schema

The following commands show how to inspect a single schema:

atlas schema inspect -u "mysql://localhost/schema"

atlas schema inspect -u "mysql://user:pass@localhost:3306/schema"

Inspect multiple schemas

The following commands show how to inspect multiple schemas:

atlas schema inspect -u "mysql://localhost" --schema schema1 --schema schema2

atlas schema inspect -u "mysql://user:pass@localhost:3306" -s schema1,schema2

Exclude schemas

The following commands show how to exclude schemas that match a glob pattern from the inspection:

atlas schema inspect -u "mysql://localhost" --exclude "internal"

atlas schema inspect -u "mysql://localhost" --exclude "schema_*"

Exclude Tables

The following commands show how to exclude tables that match a glob pattern from the inspection:

When inspecting a database (multiple schemas), the first glob pattern matches the schema name, and the second matches the table name:

atlas schema inspect -u "mysql://localhost" --exclude "*.prefix_*"

atlas schema inspect -u "mysql://localhost" --exclude "schema.table"

Exclude Table Resources

The following commands show how to exclude columns, indexes or foreign-keys that match a glob pattern from the inspection:

When inspecting a database (multiple schemas), the first glob pattern matches the schema name, and the second matches the table name:

atlas schema inspect -u "mysql://localhost" --exclude "*.*.prefix_*"

atlas schema inspect -u "mysql://localhost" --exclude "public.*.c1"

SQL Format

By default, the output of schema inspect is in the Atlas DDL. However, you can use SQL to describe the desired schema in all commands that are supported by Atlas DDL. To output the schema in SQL format, use the --format flag as follows:

atlas schema inspect -u "mysql://localhost" --format "{{ sql . }}"

JSON Format

Atlas can output a JSON document that represents the database schema. This representation allows users to use tools like jq to analyze the schema programmatically.

atlas schema inspect -u '<url>' --format '{{ json . }}'

Visualize schemas

Ariga's Explore tool, available in a web browser, can generate an Entity-Relationship Diagram (ERD) for the database schema. Visit gh.atlasgo.cloud/explore and follow the instructions.

Schema ERD

Reference

CLI Command Reference