strapi/examples/getstarted/config/environments/development/database.json

{
  "defaultConnection": "default",
  "connections": {
    "default": {
      "connector": "strapi-hook-bookshelf",
      "settings": {
        "client": "sqlite",
        "filename": ".tmp/data.db"
      },
      "options": {
        "useNullAsDefault": true
      }
    }
  }
}