diff --git a/images/tiler-server/config/providers/admin_boundaries_centroids.toml b/images/tiler-server/config/providers/admin_boundaries_centroids.toml
index 56101be2..bd237660 100644
--- a/images/tiler-server/config/providers/admin_boundaries_centroids.toml
+++ b/images/tiler-server/config/providers/admin_boundaries_centroids.toml
@@ -7,11 +7,11 @@ sql = """
 SELECT 
     ST_AsMVTGeom(geometry, !BBOX!) AS geometry,  
     ABS(osm_id) AS osm_id, 
-    admin_level, 
-    name, 
-    type, 
-    start_date, 
-    end_date, 
+    NULLIF(admin_level, '') AS admin_level, 
+    NULLIF(name, '') AS name, 
+    NULLIF(type, '') AS type, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}} 
@@ -31,11 +31,11 @@ sql = """
 SELECT 
     ST_AsMVTGeom(geometry, !BBOX!) AS geometry, 
     ABS(osm_id) AS osm_id, 
-    admin_level, 
-    name, 
-    type, 
-    start_date, 
-    end_date, 
+    NULLIF(admin_level, '') AS admin_level, 
+    NULLIF(name, '') AS name, 
+    NULLIF(type, '') AS type, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}} 
@@ -55,11 +55,11 @@ sql = """
 SELECT 
     ST_AsMVTGeom(geometry, !BBOX!) AS geometry, 
     ABS(osm_id) AS osm_id, 
-    admin_level, 
-    name, 
-    type, 
-    start_date, 
-    end_date, 
+    NULLIF(admin_level, '') AS admin_level, 
+    NULLIF(name, '') AS name, 
+    NULLIF(type, '') AS type, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}} 
@@ -79,11 +79,11 @@ sql = """
 SELECT 
     ST_AsMVTGeom(geometry, !BBOX!) AS geometry, 
     ABS(osm_id) AS osm_id, 
-    admin_level, 
-    name, 
-    type, 
-    start_date, 
-    end_date, 
+    NULLIF(admin_level, '') AS admin_level, 
+    NULLIF(name, '') AS name, 
+    NULLIF(type, '') AS type, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}} 
@@ -103,11 +103,11 @@ sql = """
 SELECT 
     ST_AsMVTGeom(geometry, !BBOX!) AS geometry, 
     ABS(osm_id) AS osm_id, 
-    admin_level, 
-    name, 
-    type, 
-    start_date, 
-    end_date, 
+    NULLIF(admin_level, '') AS admin_level, 
+    NULLIF(name, '') AS name, 
+    NULLIF(type, '') AS type, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}} 
@@ -118,7 +118,6 @@ WHERE
     AND geometry && !BBOX!
 """
 
-
 [[providers.layers]]
 name = "admin_boundaries_centroid_z13_15"
 geometry_fieldname = "geometry"
@@ -128,11 +127,11 @@ sql = """
 SELECT 
     ST_AsMVTGeom(geometry, !BBOX!) AS geometry, 
     ABS(osm_id) AS osm_id, 
-    admin_level, 
-    name, 
-    type, 
-    start_date, 
-    end_date, 
+    NULLIF(admin_level, '') AS admin_level, 
+    NULLIF(name, '') AS name, 
+    NULLIF(type, '') AS type, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}} 
@@ -152,11 +151,11 @@ sql = """
 SELECT 
     ST_AsMVTGeom(geometry, !BBOX!) AS geometry, 
     ABS(osm_id) AS osm_id, 
-    admin_level, 
-    name, 
-    type, 
-    start_date, 
-    end_date, 
+    NULLIF(admin_level, '') AS admin_level, 
+    NULLIF(name, '') AS name, 
+    NULLIF(type, '') AS type, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}} 
@@ -165,4 +164,4 @@ FROM
 WHERE 
     has_label = 0 
     AND geometry && !BBOX!
-"""
\ No newline at end of file
+"""
diff --git a/images/tiler-server/config/providers/admin_boundaries_lines.toml b/images/tiler-server/config/providers/admin_boundaries_lines.toml
index dfc680cd..bf19e45c 100644
--- a/images/tiler-server/config/providers/admin_boundaries_lines.toml
+++ b/images/tiler-server/config/providers/admin_boundaries_lines.toml
@@ -7,11 +7,11 @@ sql = """
 SELECT 
     ST_AsMVTGeom(geometry, !BBOX!) AS geometry, 
     ABS(osm_id) AS osm_id, 
-    admin_level, 
-    name, 
-    type, 
-    start_date, 
-    end_date, 
+    NULLIF(admin_level, '') AS admin_level, 
+    NULLIF(name, '') AS name, 
+    NULLIF(type, '') AS type, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -30,11 +30,11 @@ sql = """
 SELECT 
     ST_AsMVTGeom(geometry, !BBOX!) AS geometry, 
     ABS(osm_id) AS osm_id, 
-    admin_level, 
-    name, 
-    type, 
-    start_date, 
-    end_date, 
+    NULLIF(admin_level, '') AS admin_level, 
+    NULLIF(name, '') AS name, 
+    NULLIF(type, '') AS type, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -54,11 +54,11 @@ sql = """
 SELECT 
     ST_AsMVTGeom(geometry, !BBOX!) AS geometry, 
     ABS(osm_id) AS osm_id, 
-    admin_level, 
-    name, 
-    type, 
-    start_date, 
-    end_date, 
+    NULLIF(admin_level, '') AS admin_level, 
+    NULLIF(name, '') AS name, 
+    NULLIF(type, '') AS type, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -77,11 +77,11 @@ sql = """
 SELECT 
     ST_AsMVTGeom(geometry, !BBOX!) AS geometry, 
     ABS(osm_id) AS osm_id, 
-    admin_level, 
-    name, 
-    type, 
-    start_date, 
-    end_date, 
+    NULLIF(admin_level, '') AS admin_level, 
+    NULLIF(name, '') AS name, 
+    NULLIF(type, '') AS type, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -100,11 +100,11 @@ sql = """
 SELECT 
     ST_AsMVTGeom(geometry, !BBOX!) AS geometry, 
     ABS(osm_id) AS osm_id, 
-    admin_level, 
-    name, 
-    type, 
-    start_date, 
-    end_date, 
+    NULLIF(admin_level, '') AS admin_level, 
+    NULLIF(name, '') AS name, 
+    NULLIF(type, '') AS type, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -123,11 +123,11 @@ sql = """
 SELECT 
     ST_AsMVTGeom(geometry, !BBOX!) AS geometry, 
     ABS(osm_id) AS osm_id, 
-    admin_level, 
-    name, 
-    type, 
-    start_date, 
-    end_date, 
+    NULLIF(admin_level, '') AS admin_level, 
+    NULLIF(name, '') AS name, 
+    NULLIF(type, '') AS type, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -146,11 +146,11 @@ sql = """
 SELECT 
     ST_AsMVTGeom(geometry, !BBOX!) AS geometry, 
     ABS(osm_id) AS osm_id, 
-    admin_level, 
-    name, 
-    type, 
-    start_date, 
-    end_date, 
+    NULLIF(admin_level, '') AS admin_level, 
+    NULLIF(name, '') AS name, 
+    NULLIF(type, '') AS type, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
diff --git a/images/tiler-server/config/providers/admin_boundaries_maritime.toml b/images/tiler-server/config/providers/admin_boundaries_maritime.toml
index 5de4577a..ac42f1b5 100644
--- a/images/tiler-server/config/providers/admin_boundaries_maritime.toml
+++ b/images/tiler-server/config/providers/admin_boundaries_maritime.toml
@@ -35,8 +35,8 @@ SELECT
     name, 
     type, 
     maritime, 
-    start_date, 
-    end_date, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -59,8 +59,8 @@ SELECT
     name, 
     type, 
     maritime, 
-    start_date, 
-    end_date, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
diff --git a/images/tiler-server/config/providers/route_lines.toml b/images/tiler-server/config/providers/route_lines.toml
index bfab752a..3b5cf487 100644
--- a/images/tiler-server/config/providers/route_lines.toml
+++ b/images/tiler-server/config/providers/route_lines.toml
@@ -21,8 +21,8 @@ SELECT
     interval,
     duration,
     tourism,
-    start_date,
-    end_date,
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
diff --git a/images/tiler-server/config/providers/transport_lines.toml b/images/tiler-server/config/providers/transport_lines.toml
index ac6f6e1a..bd481324 100644
--- a/images/tiler-server/config/providers/transport_lines.toml
+++ b/images/tiler-server/config/providers/transport_lines.toml
@@ -7,17 +7,17 @@ sql = """
 SELECT 
     ST_AsMVTGeom(geometry, !BBOX!) AS geometry, 
     ABS(osm_id) AS osm_id, 
-    type, 
-    tunnel, 
-    bridge, 
-    ref,
-    service,
-    name,
-    electrified, 
-    highspeed, 
-    usage, 
-    start_date, 
-    end_date, 
+    NULLIF(type, '') AS type, 
+    NULLIF(tunnel, '') AS tunnel, 
+    NULLIF(bridge, '') AS bridge, 
+    NULLIF(ref, '') AS ref,
+    NULLIF(service, '') AS service,
+    NULLIF(name, '') AS name,
+    NULLIF(electrified, '') AS electrified, 
+    NULLIF(highspeed, '') AS highspeed, 
+    NULLIF(usage, '') AS usage, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -36,16 +36,16 @@ sql = """
 SELECT 
     ST_AsMVTGeom(geometry, !BBOX!) AS geometry, 
     ABS(osm_id) AS osm_id,
-    ref, 
-    class, 
-    type, 
-    service,
-    name,
-    electrified, 
-    highspeed, 
-    usage, 
-    start_date, 
-    end_date, 
+    NULLIF(ref, '') AS ref, 
+    NULLIF(class, '') AS class, 
+    NULLIF(type, '') AS type, 
+    NULLIF(service, '') AS service,
+    NULLIF(name, '') AS name,
+    NULLIF(electrified, '') AS electrified, 
+    NULLIF(highspeed, '') AS highspeed, 
+    NULLIF(usage, '') AS usage, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -64,16 +64,16 @@ sql = """
 SELECT 
     ST_AsMVTGeom(geometry, !BBOX!) AS geometry, 
     ABS(osm_id) AS osm_id, 
-    ref, 
-    class, 
-    type, 
-    service, 
-    name,
-    electrified, 
-    highspeed, 
-    usage, 
-    start_date, 
-    end_date, 
+    NULLIF(ref, '') AS ref, 
+    NULLIF(class, '') AS class, 
+    NULLIF(type, '') AS type, 
+    NULLIF(service, '') AS service, 
+    NULLIF(name, '') AS name,
+    NULLIF(electrified, '') AS electrified, 
+    NULLIF(highspeed, '') AS highspeed, 
+    NULLIF(usage, '') AS usage, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -92,16 +92,16 @@ sql = """
 SELECT 
     ST_AsMVTGeom(geometry, !BBOX!) AS geometry, 
     ABS(osm_id) AS osm_id, 
-    ref, 
-    class, 
-    type, 
-    service, 
-    name,
-    electrified, 
-    highspeed, 
-    usage, 
-    start_date, 
-    end_date, 
+    NULLIF(ref, '') AS ref, 
+    NULLIF(class, '') AS class, 
+    NULLIF(type, '') AS type, 
+    NULLIF(service, '') AS service, 
+    NULLIF(name, '') AS name,
+    NULLIF(electrified, '') AS electrified, 
+    NULLIF(highspeed, '') AS highspeed, 
+    NULLIF(usage, '') AS usage, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -120,16 +120,16 @@ sql = """
 SELECT 
     ST_AsMVTGeom(geometry, !BBOX!) AS geometry, 
     ABS(osm_id) AS osm_id,  
-    ref, 
-    class, 
-    type, 
-    service, 
-    name,
-    electrified, 
-    highspeed, 
-    usage, 
-    start_date, 
-    end_date, 
+    NULLIF(ref, '') AS ref, 
+    NULLIF(class, '') AS class, 
+    NULLIF(type, '') AS type, 
+    NULLIF(service, '') AS service, 
+    NULLIF(name, '') AS name,
+    NULLIF(electrified, '') AS electrified, 
+    NULLIF(highspeed, '') AS highspeed, 
+    NULLIF(usage, '') AS usage, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
diff --git a/images/tiler-server/config/providers/water_areas.centroids.toml b/images/tiler-server/config/providers/water_areas.centroids.toml
index e503606a..71e1c025 100644
--- a/images/tiler-server/config/providers/water_areas.centroids.toml
+++ b/images/tiler-server/config/providers/water_areas.centroids.toml
@@ -10,8 +10,8 @@ SELECT
     name, 
     type, 
     area, 
-    start_date, 
-    end_date, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -33,8 +33,8 @@ SELECT
     name, 
     type, 
     area, 
-    start_date, 
-    end_date, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -57,8 +57,8 @@ SELECT
     name, 
     type, 
     area, 
-    start_date, 
-    end_date, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -81,8 +81,8 @@ SELECT
     name, 
     type, 
     area, 
-    start_date, 
-    end_date, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -104,8 +104,8 @@ SELECT
     name, 
     type, 
     area, 
-    start_date, 
-    end_date, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -129,8 +129,8 @@ SELECT
     name, 
     type, 
     area, 
-    start_date, 
-    end_date, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
diff --git a/images/tiler-server/config/providers/water_areas.toml b/images/tiler-server/config/providers/water_areas.toml
index 4e632dd0..1f9f355e 100644
--- a/images/tiler-server/config/providers/water_areas.toml
+++ b/images/tiler-server/config/providers/water_areas.toml
@@ -10,8 +10,8 @@ SELECT
     name, 
     type, 
     area, 
-    start_date, 
-    end_date, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -33,8 +33,8 @@ SELECT
     name, 
     type, 
     area, 
-    start_date, 
-    end_date, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -57,8 +57,8 @@ SELECT
     name, 
     type, 
     area, 
-    start_date, 
-    end_date, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -80,8 +80,8 @@ SELECT
     name, 
     type, 
     area, 
-    start_date, 
-    end_date, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -103,8 +103,8 @@ SELECT
     name, 
     type, 
     area, 
-    start_date, 
-    end_date, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -126,8 +126,8 @@ SELECT
     name, 
     type, 
     area, 
-    start_date, 
-    end_date, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
@@ -149,8 +149,8 @@ SELECT
     name, 
     type, 
     area, 
-    start_date, 
-    end_date, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}
diff --git a/images/tiler-server/config/providers/water_lines.toml b/images/tiler-server/config/providers/water_lines.toml
index 387c030f..2d442526 100644
--- a/images/tiler-server/config/providers/water_lines.toml
+++ b/images/tiler-server/config/providers/water_lines.toml
@@ -10,8 +10,8 @@ SELECT
     name, 
     type, 
     bridge, 
-    start_date, 
-    end_date, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}} 
@@ -33,8 +33,8 @@ SELECT
     name, 
     type, 
     bridge, 
-    start_date, 
-    end_date, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}} 
@@ -56,8 +56,8 @@ SELECT
     name, 
     type, 
     bridge, 
-    start_date, 
-    end_date, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}} 
@@ -79,8 +79,8 @@ SELECT
     name, 
     type, 
     bridge, 
-    start_date, 
-    end_date, 
+    NULLIF(start_date, '') AS start_date, 
+    NULLIF(end_date, '') AS end_date, 
     isodatetodecimaldate(pad_date(start_date, 'start'), FALSE) AS start_decdate, 
     isodatetodecimaldate(pad_date(end_date, 'end'), FALSE) AS end_decdate,
     {{LENGUAGES}}