Schema inspection

Inspect tables and columns

Classic migrations read through Database. FluentMigration exposes Schema for queries and Context for the full provider API. A fluent authoring method runs before its queued operations: an inspection cannot see a table merely queued earlier in the same builder.

if (!Database.ColumnExists("Users", "Email"))
    Database.AddColumn("Users", new Column("Email", DbType.String, 320));

if (!Schema.Table("Users").ColumnExists("Email"))
    migration.Create.Column("Email").OnTable("Users").AsString(320);

Read ordered constraints

GetColumns returns inferred column attributes, not primary/unique membership flags. It is obsolete because native types and defaults cannot be mapped back to exact .NET definitions; use migration history for the original definition. Read typed table constraints to retain ordered composite keys. Unique indexes remain index metadata. MySQL/MariaDB catalogs cannot distinguish every original unique-index versus UNIQUE-clause authoring choice.

var constraints = Database.GetTableConstraints("Users");
foreach (var constraint in constraints)
    Console.WriteLine(constraint.Name);

var constraints = Schema.Table("Users").ConstraintDefinitions();
foreach (var constraint in constraints)
    Console.WriteLine(constraint.Name);

Create a view

ViewField selects columns from a base table. The alternative IViewElement overload represents explicit columns and joins. View definitions are provider-dependent and outside SQL preview and automatic reversal. Write a provider-appropriate DROP VIEW statement in the reverse method, and manage dependent views when changing their underlying tables.

Database.AddView("UserNames", "Users", new ViewField("Id"), new ViewField("Name"));

migration.Create.View("UserNames").FromTable("Users")
    .WithFields(new ViewField("Id"), new ViewField("Name"));

Reads and portability

Dispose readers and commands obtained from the provider. Fluent Schema.Query and Schema.Table(name).Select accept a reader callback and handle disposal. Use Schema.Table(name).SelectScalar(columns, where) for a scalar selection. Use provider quoting helpers for table and column identifiers separately: quoting a table may introduce schema qualification, which is not valid for a column expression.

Metadata fidelity depends on the provider. Unsupported readers throw instead of pretending that an empty schema was found. A successful existence check is not a full schema-drift report.