Fixes SQL providers for returning the correct results for constraints

src/Umbraco.Core/Persistence/SqlSyntax/ISqlSyntaxProvider.cs

@@ -78,9 +78,32 @@ namespace Umbraco.Core.Persistence.SqlSyntax
 
         IEnumerable<string> GetTablesInSchema(Database db);
         IEnumerable<ColumnInfo> GetColumnsInSchema(Database db);
+
+        /// <summary>
+        /// Returns all constraints defined in the database (Primary keys, foreign keys, unique constraints...) (does not include indexes)
+        /// </summary>
+        /// <param name="db"></param>
+        /// <returns>
+        /// A Tuple containing: TableName, ConstraintName
+        /// </returns>
         IEnumerable<Tuple<string, string>> GetConstraintsPerTable(Database db);
+
+        /// <summary>
+        /// Returns all constraints defined in the database (Primary keys, foreign keys, unique constraints...) (does not include indexes)
+        /// </summary>
+        /// <param name="db"></param>
+        /// <returns>
+        /// A Tuple containing: TableName, ColumnName, ConstraintName
+        /// </returns>
         IEnumerable<Tuple<string, string, string>> GetConstraintsPerColumn(Database db);
 
+        /// <summary>
+        /// Returns all defined Indexes in the database excluding primary keys
+        /// </summary>
+        /// <param name="db"></param>
+        /// <returns>
+        /// A Tuple containing: TableName, IndexName, ColumnName, IsUnique
+        /// </returns>
         IEnumerable<Tuple<string, string, string, bool>> GetDefinedIndexes(Database db);
     }
-}
+}