test.mml

    # Normal YAML highlighting:
    _parts:
      srid: &srid "3857"
      # YAML comment
      world: &world
        - -180
      extents: &extents
        extent: *world
        srs-name: *srid
    scale: 1
    interactivity: false

    Layer:
      - id: water-lines-low-zoom
        geometry: linestring
        geometry2: "string"
        Datasource:
          <<: *osm2pgsql
          table: |-
            -- Highlighting the table SQL by including PostgreSQL highlighting:
            (SELECT
                way,
                -- SQL comment
                waterway,
                CASE WHEN tags->'intermittent' IN ('yes')
                  OR tags->'seasonal' IN ('yes', 'spring', 'summer', 'autumn', 'winter', 'wet_season', 'dry_season')
                  THEN 'yes' ELSE 'no' END AS int_intermittent
              FROM planet_osm_line
              WHERE waterway = 'river'
            ) AS water_lines_low_zoom
        properties:
          minzoom: 8 # number
          maxzoom: 11 # number