{
    "select": {
        "table" : [
            "field1",
            "field2"
        ]
    },
    "join" : {
        "left" : "field_to_index",
        "right" : {
            "db" : "tableName",
            "index" : "field_to_index"
        }
    },
    "condition" : {
        "field1" : "equal",
        "field2" : "equal"
    }
}