title: How do I use MigrationBuilder DeleteData to delete all rows during a migration?
body: <p>The <a href="https://docs.microsoft.com/en-us/dotnet/api/microsoft.entityframeworkcore.migrations.migrationbuilder.deletedata?view=efcore-2.0#Microsoft_EntityFrameworkCore_Migrations_MigrationBuilder_DeleteData_System_String_System_String_System_Object_System_String_" rel="noreferrer">documentation</a> is not very helpful - just a list of function signatures, of which the simplest is:</p>
  
  <blockquote>
    <p>public virtual OperationBuilder DeleteData (string table, string keyColumn, object keyValue, string schema = null);</p>
  </blockquote>
  
  <p>I am fairly sure I can work out what goes in table, keyColumn and schema, but what value should I put in keyValue if I want to delete all rows?</p>