A constraint containing no columns has been defined.

How to fix

Ensure that you have at least one column defined per constraint.

Problem example:

{
  "tables": [
    {
      "schema": "dbo",
      "name": "Users",
      "constraints": [
        {
          "type": "Unique",
          "columns": []                  // Empty columns array
        }
      ]
    }
  ]
}

Ensure that you have at least one column defined per constraint:

{
  "tables": [
    {
      "schema": "dbo",
      "name": "Users",
      "constraints": [
        {
          "type": "Unique",
          "columns": ["UserId"]          // Added column reference
        }
      ]
    }
  ]
}