The same column has been defined in a constraint more than once.

How to fix

Ensure that you have defined each column only once.

Problem example:

{
  "tables": [
    {
      "schema": "Person",
      "name": "Address",
      "columns": [
        {
          "name": "AddressLine1",
          "dataset": "AddressesUnique",
          "deterministic": false
        },
        {
          "name": "City",
          "deterministic": false,
          "maxLength": 15
        }
      ],
      "constraints": [
        {
          "type": "Unique",
          "columns": [
            "AddressLine1",
            "AddressLine1"              // Duplicate column in constraint
          ]
        }
      ]
    }
  ]
}

Ensure that you have defined each column only once:

{
  "tables": [
    {
      "schema": "Person",
      "name": "Address",
      "columns": [
        {
          "name": "AddressLine1",
          "dataset": "AddressesUnique",
          "deterministic": false
        },
        {
          "name": "City",
          "deterministic": false,
          "maxLength": 15
        }
      ],
      "constraints": [
        {
          "type": "Unique",
          "columns": [
            "AddressLine1"              // Single column reference
          ]
        }
      ]
    }
  ]
}

Multi-column constraint example:

{
  "tables": [
    {
      "schema": "Person",
      "name": "Address",
      "columns": [
        {
          "name": "City",
          "deterministic": false,
          "maxLength": 15
        },
        {
          "name": "AddressLine1",
          "dataset": "AddressesUnique",
          "deterministic": false
        },
        {
          "name": "PostalCode",
          "dataset": "PostalCodes",
          "deterministic": false
        }
      ],
      "constraints": [
        {
          "type": "Unique",
          "columns": [
            "AddressLine1",
            "City",
            "PostalCode"
          ]
        }
      ]
    }
  ]
}