diff --git a/src/main/java/de/avatic/lcc/database/dialect/MSSQLDialectProvider.java b/src/main/java/de/avatic/lcc/database/dialect/MSSQLDialectProvider.java
index f5cdacd..100edf3 100644
--- a/src/main/java/de/avatic/lcc/database/dialect/MSSQLDialectProvider.java
+++ b/src/main/java/de/avatic/lcc/database/dialect/MSSQLDialectProvider.java
@@ -148,49 +148,32 @@ public class MSSQLDialectProvider implements SqlDialectProvider {
         );
     }
 
-    /**
-     * Builds MSSQL INSERT with IF NOT EXISTS check.
-     *
-     * <p>MSSQL doesn't have INSERT IGNORE, so we use IF NOT EXISTS.</p>
-     *
-     * <p>Example generated SQL:</p>
-     * <pre>
-     * IF NOT EXISTS (SELECT 1 FROM table WHERE key1 = ? AND key2 = ?)
-     * INSERT INTO table (col1, col2, col3) VALUES (?, ?, ?)
-     * </pre>
-     *
-     * @param tableName     target table name
-     * @param columns       columns to insert
-     * @param uniqueColumns columns to check for existence
-     * @return MSSQL INSERT with IF NOT EXISTS
-     */
     @Override
     public String buildInsertIgnoreStatement(
             String tableName,
             List<String> columns,
             List<String> uniqueColumns
     ) {
-        if (tableName == null || columns.isEmpty() || uniqueColumns.isEmpty()) {
-            throw new IllegalArgumentException("tableName, columns, and uniqueColumns must not be empty");
-        }
-
-        String whereClause = uniqueColumns.stream()
-                .map(col -> col + " = ?")
-                .collect(Collectors.joining(" AND "));
-
         String columnList = String.join(", ", columns);
-        String placeholders = columns.stream()
-                .map(col -> "?")
+        String placeholders = columns.stream().map(c -> "?").collect(Collectors.joining(", "));
+        String uniqueCondition = uniqueColumns.stream()
+                .map(c -> String.format("target.%s = source.%s", c, c))
+                .collect(Collectors.joining(" AND "));
+        String sourceColumns = columns.stream()
+                .map(c -> String.format("source.%s", c))
                 .collect(Collectors.joining(", "));
 
         return String.format(
-                "IF NOT EXISTS (SELECT 1 FROM %s WHERE %s) " +
-                        "INSERT INTO %s (%s) VALUES (%s)",
-                tableName,
-                whereClause,
+                "MERGE INTO %s AS target " +
+                        "USING (SELECT %s) AS source (%s) " +
+                        "ON %s " +
+                        "WHEN NOT MATCHED THEN INSERT (%s) VALUES (%s);",
                 tableName,
+                placeholders,
                 columnList,
-                placeholders
+                uniqueCondition,
+                columnList,
+                sourceColumns
         );
     }
 
diff --git a/src/main/java/de/avatic/lcc/repositories/country/CountryPropertyRepository.java b/src/main/java/de/avatic/lcc/repositories/country/CountryPropertyRepository.java
index bd91a78..cd0f6c2 100644
--- a/src/main/java/de/avatic/lcc/repositories/country/CountryPropertyRepository.java
+++ b/src/main/java/de/avatic/lcc/repositories/country/CountryPropertyRepository.java
@@ -150,7 +150,6 @@ public class CountryPropertyRepository {
                     type.external_mapping_id as externalMappingId,
                     type.validation_rule as validationRule,
                     type.is_required as is_required,
-                    type.is_required as is_required,
                     type.description as description,
                     type.property_group as propertyGroup,
                     type.sequence_number as sequenceNumber,
@@ -159,7 +158,8 @@ public class CountryPropertyRepository {
                 FROM country_property_type AS type
                 LEFT JOIN country_property AS cp ON cp.country_property_type_id = type.id AND cp.country_id = ?
                 LEFT JOIN property_set AS ps ON ps.id = cp.property_set_id AND ps.state IN ('DRAFT', 'VALID')
-                GROUP BY type.id, type.name, type.data_type, type.external_mapping_id, type.validation_rule
+                GROUP BY type.id, type.name, type.data_type, type.external_mapping_id, type.validation_rule,
+                         type.is_required, type.description, type.property_group, type.sequence_number
                 HAVING MAX(CASE WHEN ps.state = 'DRAFT' THEN cp.property_value END) IS NOT NULL
                     OR MAX(CASE WHEN ps.state = 'VALID' THEN cp.property_value END) IS NOT NULL;
                 """;
diff --git a/src/test/java/de/avatic/lcc/repositories/country/CountryPropertyRepositoryIntegrationTest.java b/src/test/java/de/avatic/lcc/repositories/country/CountryPropertyRepositoryIntegrationTest.java
index 19d858f..3ca75b3 100644
--- a/src/test/java/de/avatic/lcc/repositories/country/CountryPropertyRepositoryIntegrationTest.java
+++ b/src/test/java/de/avatic/lcc/repositories/country/CountryPropertyRepositoryIntegrationTest.java
@@ -142,9 +142,6 @@ class CountryPropertyRepositoryIntegrationTest extends AbstractRepositoryIntegra
 
     @Test
     void testListPropertiesByCountryId() {
-        // Skip on MSSQL - listPropertiesByCountryId() has incomplete GROUP BY clause (missing is_required, description, property_group, sequence_number)
-        org.junit.Assume.assumeTrue("Skipping listPropertiesByCountryId on MSSQL (SQL GROUP BY bug in repository)", isMysql());
-
         // Given: Create properties for country
         createTestCountryProperty(testDraftSetId, testCountryId, testPropertyTypeId, "45");
         createTestCountryProperty(testValidSetId, testCountryId, testPropertyTypeId, "30");
@@ -188,9 +185,6 @@ class CountryPropertyRepositoryIntegrationTest extends AbstractRepositoryIntegra
 
     @Test
     void testFillDraft() {
-        // Skip on MSSQL - buildInsertIgnoreStatement needs fix for parameter ordering in IF NOT EXISTS pattern
-        org.junit.Assume.assumeTrue("Skipping fillDraft on MSSQL (known issue with INSERT IGNORE)", isMysql());
-
         // Given: Create properties in valid set for multiple property types
         Integer propertyType2 = getPropertyTypeId(CountryPropertyMappingId.WAGE.name());
         createTestCountryProperty(testValidSetId, testCountryId, testPropertyTypeId, "30");
diff --git a/src/test/java/de/avatic/lcc/repositories/properties/PropertyRepositoryIntegrationTest.java b/src/test/java/de/avatic/lcc/repositories/properties/PropertyRepositoryIntegrationTest.java
index c61fe02..885b121 100644
--- a/src/test/java/de/avatic/lcc/repositories/properties/PropertyRepositoryIntegrationTest.java
+++ b/src/test/java/de/avatic/lcc/repositories/properties/PropertyRepositoryIntegrationTest.java
@@ -189,9 +189,6 @@ class PropertyRepositoryIntegrationTest extends AbstractRepositoryIntegrationTes
 
     @Test
     void testFillDraft() {
-        // Skip on MSSQL - buildInsertIgnoreStatement needs fix for parameter ordering in IF NOT EXISTS pattern
-        org.junit.Assume.assumeTrue("Skipping fillDraft on MSSQL (known issue with INSERT IGNORE)", isMysql());
-
         // Given: Create properties in valid set
         Integer propertyType2 = getPropertyTypeId(SystemPropertyMappingId.WORKDAYS.name());
         createTestProperty(testValidSetId, testPropertyTypeId, "30");
@@ -220,9 +217,6 @@ class PropertyRepositoryIntegrationTest extends AbstractRepositoryIntegrationTes
 
     @Test
     void testFillDraftIgnoresDuplicates() {
-        // Skip on MSSQL - buildInsertIgnoreStatement needs fix for parameter ordering in IF NOT EXISTS pattern
-        org.junit.Assume.assumeTrue("Skipping fillDraft on MSSQL (known issue with INSERT IGNORE)", isMysql());
-
         // Given: Create property in valid set
         createTestProperty(testValidSetId, testPropertyTypeId, "30");
 
diff --git a/src/test/java/de/avatic/lcc/repositories/users/AppRepositoryIntegrationTest.java b/src/test/java/de/avatic/lcc/repositories/users/AppRepositoryIntegrationTest.java
index 983c60b..d535e99 100644
--- a/src/test/java/de/avatic/lcc/repositories/users/AppRepositoryIntegrationTest.java
+++ b/src/test/java/de/avatic/lcc/repositories/users/AppRepositoryIntegrationTest.java
@@ -163,9 +163,6 @@ class AppRepositoryIntegrationTest extends AbstractRepositoryIntegrationTest {
 
     @Test
     void testAppWithGroups() {
-        // Skip on MSSQL - buildInsertIgnoreStatement needs fix for parameter ordering
-        org.junit.Assume.assumeTrue("Skipping app-group mapping on MSSQL (known issue with INSERT IGNORE)", isMysql());
-
         // Given: App with groups
         App app = createTestApp("App with Groups", "grouped_client", "grouped_secret");
         Group group1 = new Group();
@@ -191,9 +188,6 @@ class AppRepositoryIntegrationTest extends AbstractRepositoryIntegrationTest {
 
     @Test
     void testUpdateAppGroups() {
-        // Skip on MSSQL - buildInsertIgnoreStatement needs fix for parameter ordering
-        org.junit.Assume.assumeTrue("Skipping app-group mapping on MSSQL (known issue with INSERT IGNORE)", isMysql());
-
         // Given: App with one group
         App app = createTestApp("Group Update Test", "group_update_client", "group_update_secret");
         Group group1 = new Group();
@@ -217,9 +211,6 @@ class AppRepositoryIntegrationTest extends AbstractRepositoryIntegrationTest {
 
     @Test
     void testDeleteAppCascadesGroupMappings() {
-        // Skip on MSSQL - buildInsertIgnoreStatement needs fix for parameter ordering
-        org.junit.Assume.assumeTrue("Skipping app-group mapping on MSSQL (known issue with INSERT IGNORE)", isMysql());
-
         // Given: App with groups
         App app = createTestApp("Cascade Delete Test", "cascade_client", "cascade_secret");
         Group group1 = new Group();