diff --git a/qlite/src/column.vala b/qlite/src/column.vala
index 048446fb..9c201885 100644
--- a/qlite/src/column.vala
+++ b/qlite/src/column.vala
@@ -4,12 +4,12 @@ namespace Qlite {
 
 public abstract class Column<T> {
     public string name { get; private set; }
-    public string default { get; set; }
+    public string? default { get; set; }
     public int sqlite_type { get; private set; }
     public bool primary_key { get; set; }
     public bool auto_increment { get; set; }
     public bool unique { get; set; }
-    public bool not_null { get; set; }
+    public virtual bool not_null { get; set; }
     public long min_version { get; set; default = -1; }
     public long max_version { get; set; default = long.MAX; }
 
@@ -43,7 +43,7 @@ public abstract class Column<T> {
         }
         if (not_null) res += " NOT NULL";
         if (unique) res += " UNIQUE";
-        if (default != null) res += @" DEFAULT $default";
+        if (default != null) res += @" DEFAULT $((!) default)";
 
         return res;
     }
@@ -122,13 +122,33 @@ public abstract class Column<T> {
 
         internal override void bind(Statement stmt, int index, string? value) {
             if (value != null) {
-                stmt.bind_text(index, value);
+                stmt.bind_text(index, (!) value);
             } else {
                 stmt.bind_null(index);
             }
         }
     }
 
+    public class NonNullText : Column<string> {
+        public NonNullText(string name) {
+            base(name, TEXT);
+        }
+
+        public override bool not_null { get { return true; } set {} }
+
+        public override string get(Row row) {
+            return (!)row.get_text(name);
+        }
+
+        public override bool is_null(Row row) {
+            return false;
+        }
+
+        internal override void bind(Statement stmt, int index, string value) {
+            stmt.bind_text(index, (!) value);
+        }
+    }
+
     public class BoolText : Column<bool> {
         public BoolText(string name) {
             base(name, TEXT);
diff --git a/qlite/src/database.vala b/qlite/src/database.vala
index 89eda204..0427df16 100644
--- a/qlite/src/database.vala
+++ b/qlite/src/database.vala
@@ -17,11 +17,11 @@ public class Database {
     private string file_name;
     private Sqlite.Database db;
     private long expected_version;
-    private Table[] tables;
+    private Table[]? tables;
 
-    private Column<string> meta_name = new Column.Text("name") { primary_key = true };
+    private Column<string?> meta_name = new Column.Text("name") { primary_key = true };
     private Column<long> meta_int_val = new Column.Long("int_val");
-    private Column<string> meta_text_val = new Column.Text("text_val");
+    private Column<string?> meta_text_val = new Column.Text("text_val");
     private Table meta_table;
 
     public bool debug = false;
diff --git a/qlite/src/delete_builder.vala b/qlite/src/delete_builder.vala
index 8e4afb06..5483b652 100644
--- a/qlite/src/delete_builder.vala
+++ b/qlite/src/delete_builder.vala
@@ -5,12 +5,12 @@ namespace Qlite {
 public class DeleteBuilder : StatementBuilder {
 
     // DELETE FROM [...]
-    private Table table;
+    private Table? table;
     private string table_name;
 
     // WHERE [...]
-    private string selection;
-    private StatementBuilder.Field[] selection_args;
+    private string selection = "1";
+    private StatementBuilder.AbstractField[] selection_args = {};
 
     internal DeleteBuilder(Database db) {
         base(db);
@@ -29,35 +29,22 @@ public class DeleteBuilder : StatementBuilder {
     }
 
     public DeleteBuilder where(string selection, string[]? selection_args = null) throws DatabaseError {
-        if (this.selection != null) throw new DatabaseError.ILLEGAL_QUERY("selection was already done, but where() was called.");
+        if (this.selection != "1") throw new DatabaseError.ILLEGAL_QUERY("selection was already done, but where() was called.");
         this.selection = selection;
-        if (selection_args != null) {
-            this.selection_args = new StatementBuilder.Field[selection_args.length];
-            for (int i = 0; i < selection_args.length; i++) {
-                this.selection_args[i] = new StatementBuilder.StringField(selection_args[i]);
-            }
+        foreach (string arg in selection_args) {
+            this.selection_args += new StatementBuilder.StringField(arg);
         }
         return this;
     }
 
     public DeleteBuilder with<T>(Column<T> column, string comp, T value) {
-        if (selection == null) {
-            selection = @"$(column.name) $comp ?";
-            selection_args = { new StatementBuilder.Field<T>(column, value) };
-        } else {
-            selection = @"($selection) AND $(column.name) $comp ?";
-            StatementBuilder.Field[] selection_args_new = new StatementBuilder.Field[selection_args.length+1];
-            for (int i = 0; i < selection_args.length; i++) {
-                selection_args_new[i] = selection_args[i];
-            }
-            selection_args_new[selection_args.length] = new Field<T>(column, value);
-            selection_args = selection_args_new;
-        }
+        selection_args += new Field<T>(column, value);
+        selection = @"($selection) AND $(column.name) $comp ?";
         return this;
     }
 
     internal override Statement prepare() throws DatabaseError {
-        Statement stmt = db.prepare(@"DELETE FROM $table_name $(selection != null ? @"WHERE $selection": "")");
+        Statement stmt = db.prepare(@"DELETE FROM $table_name WHERE $selection");
         for (int i = 0; i < selection_args.length; i++) {
             selection_args[i].bind(stmt, i+1);
         }
diff --git a/qlite/src/insert_builder.vala b/qlite/src/insert_builder.vala
index 51030294..91388f69 100644
--- a/qlite/src/insert_builder.vala
+++ b/qlite/src/insert_builder.vala
@@ -6,14 +6,14 @@ public class InsertBuilder : StatementBuilder {
 
     // INSERT [OR ...]
     private bool replace_val;
-    private string or_val;
+    private string? or_val;
 
     // INTO [...]
     private Table table;
     private string table_name;
 
     // VALUES [...]
-    private StatementBuilder.Field[] fields;
+    private StatementBuilder.AbstractField[] fields = {};
 
     internal InsertBuilder(Database db) {
         base(db);
@@ -41,31 +41,13 @@ public class InsertBuilder : StatementBuilder {
     }
 
     public InsertBuilder value<T>(Column<T> column, T value) {
-        if (fields == null) {
-            fields = { new StatementBuilder.Field<T>(column, value) };
-        } else {
-            StatementBuilder.Field[] fields_new = new StatementBuilder.Field[fields.length+1];
-            for (int i = 0; i < fields.length; i++) {
-                fields_new[i] = fields[i];
-            }
-            fields_new[fields.length] = new Field<T>(column, value);
-            fields = fields_new;
-        }
+        fields += new Field<T>(column, value);
         return this;
     }
 
     public InsertBuilder value_null<T>(Column<T> column) throws DatabaseError {
         if (column.not_null) throw new DatabaseError.ILLEGAL_QUERY(@"Can't set non-null column $(column.name) to null");
-        if (fields == null) {
-            fields = { new NullField<T>(column) };
-        } else {
-            StatementBuilder.Field[] fields_new = new StatementBuilder.Field[fields.length+1];
-            for (int i = 0; i < fields.length; i++) {
-                fields_new[i] = fields[i];
-            }
-            fields_new[fields.length] = new NullField<T>(column);
-            fields = fields_new;
-        }
+        fields += new NullField<T>(column);
         return this;
     }
 
@@ -77,11 +59,11 @@ public class InsertBuilder : StatementBuilder {
                 value_qs += ", ";
                 fields_text += ", ";
             }
-            fields_text += fields[i].column.name;
+            fields_text += ((!)fields[i].column).name;
             value_qs += "?";
         }
         string sql = replace_val ? "REPLACE" : "INSERT";
-        if (!replace_val && or_val != null) sql += @" OR $or_val";
+        if (!replace_val && or_val != null) sql += @" OR $((!)or_val)";
         sql += @" INTO $table_name ( $fields_text ) VALUES ($value_qs)";
         Statement stmt = db.prepare(sql);
         for (int i = 0; i < fields.length; i++) {
diff --git a/qlite/src/query_builder.vala b/qlite/src/query_builder.vala
index 06232fc1..f46fe98c 100644
--- a/qlite/src/query_builder.vala
+++ b/qlite/src/query_builder.vala
@@ -7,18 +7,18 @@ public class QueryBuilder : StatementBuilder {
 
     // SELECT [...]
     private string column_selector = "*";
-    private Column[] columns;
+    private Column[] columns = {};
 
     // FROM [...]
-    private Table table;
-    private string table_name;
+    private Table? table;
+    private string? table_name;
 
     // WHERE [...]
-    private string selection;
-    private StatementBuilder.Field[] selection_args;
+    private string selection = "1";
+    private StatementBuilder.AbstractField[] selection_args = {};
 
     // ORDER BY [...]
-    private OrderingTerm[] order_by_terms;
+    private OrderingTerm[]? order_by_terms = {};
 
     // LIMIT [...]
     private int limit_val;
@@ -27,9 +27,9 @@ public class QueryBuilder : StatementBuilder {
         base(db);
     }
 
-    public QueryBuilder select(Column[]? columns = null) {
+    public QueryBuilder select(Column[] columns = {}) {
         this.columns = columns;
-        if (columns != null) {
+        if (columns.length == 0) {
             for (int i = 0; i < columns.length; i++) {
                 if (column_selector == "*") {
                     column_selector = columns[0].name;
@@ -44,7 +44,7 @@ public class QueryBuilder : StatementBuilder {
     }
 
     public QueryBuilder select_string(string column_selector) {
-        this.columns = null;
+        this.columns = {};
         this.column_selector = column_selector;
         return this;
     }
@@ -61,32 +61,19 @@ public class QueryBuilder : StatementBuilder {
         return this;
     }
 
-    public QueryBuilder where(string selection, string[]? selection_args = null) throws DatabaseError {
-        if (this.selection != null) throw new DatabaseError.ILLEGAL_QUERY("selection was already done, but where() was called.");
+    public QueryBuilder where(string selection, string[] selection_args = {}) throws DatabaseError {
+        if (this.selection != "1") throw new DatabaseError.ILLEGAL_QUERY("selection was already done, but where() was called.");
         this.selection = selection;
-        if (selection_args != null) {
-            this.selection_args = new StatementBuilder.Field[selection_args.length];
-            for (int i = 0; i < selection_args.length; i++) {
-                this.selection_args[i] = new StatementBuilder.StringField(selection_args[i]);
-            }
+        foreach (string arg in selection_args) {
+            this.selection_args += new StatementBuilder.StringField(arg);
         }
         return this;
     }
 
     public QueryBuilder with<T>(Column<T> column, string comp, T value) {
         if ((column.unique || column.primary_key) && comp == "=") single_result = true;
-        if (selection == null) {
-            selection = @"$(column.name) $comp ?";
-            selection_args = { new StatementBuilder.Field<T>(column, value) };
-        } else {
-            selection = @"($selection) AND $(column.name) $comp ?";
-            StatementBuilder.Field[] selection_args_new = new StatementBuilder.Field[selection_args.length+1];
-            for (int i = 0; i < selection_args.length; i++) {
-                selection_args_new[i] = selection_args[i];
-            }
-            selection_args_new[selection_args.length] = new Field<T>(column, value);
-            selection_args = selection_args_new;
-        }
+        selection_args += new Field<T>(column, value);
+        selection = @"($selection) AND $(column.name) $comp ?";
         return this;
     }
 
@@ -100,26 +87,13 @@ public class QueryBuilder : StatementBuilder {
         return this;
     }
 
-    private void add_order_by(OrderingTerm term) {
-        if (order_by_terms == null) {
-            order_by_terms = { term };
-        } else {
-            OrderingTerm[] order_by_terms_new = new OrderingTerm[order_by_terms.length+1];
-            for (int i = 0; i < order_by_terms.length; i++) {
-                order_by_terms_new[i] = order_by_terms[i];
-            }
-            order_by_terms_new[order_by_terms.length] = term;
-            order_by_terms = order_by_terms_new;
-        }
-    }
-
     public QueryBuilder order_by(Column column, string dir = "ASC") {
-        add_order_by(new OrderingTerm(column, dir));
+        order_by_terms += new OrderingTerm(column, dir);
         return this;
     }
 
     public QueryBuilder order_by_name(string name, string dir) {
-        add_order_by(new OrderingTerm.by_name(name, dir));
+        order_by_terms += new OrderingTerm.by_name(name, dir);
         return this;
     }
 
@@ -131,12 +105,12 @@ public class QueryBuilder : StatementBuilder {
     public int64 count() throws DatabaseError {
         this.column_selector = @"COUNT($column_selector) AS count";
         this.single_result = true;
-        return row_().get_integer("count");
+        return row().get_integer("count");
     }
 
     private Row? row_() throws DatabaseError {
         if (!single_result) throw new DatabaseError.NON_UNIQUE("query is not suited to return a single row, but row() was called.");
-        return iterator().next_value();
+        return iterator().get_next();
     }
 
     public RowOption row() throws DatabaseError {
@@ -148,7 +122,7 @@ public class QueryBuilder : StatementBuilder {
     }
 
     internal override Statement prepare() throws DatabaseError {
-        Statement stmt = db.prepare(@"SELECT $column_selector FROM $table_name $(selection != null ? @"WHERE $selection" : "") $(order_by_terms != null ? OrderingTerm.all_to_string(order_by_terms) : "") $(limit_val > 0 ? @" LIMIT $limit_val" : "")");
+        Statement stmt = db.prepare(@"SELECT $column_selector $(table_name == null ? "" : @"FROM $((!) table_name)") WHERE $selection $(OrderingTerm.all_to_string(order_by_terms)) $(limit_val > 0 ? @" LIMIT $limit_val" : "")");
         for (int i = 0; i < selection_args.length; i++) {
             selection_args[i].bind(stmt, i+1);
         }
@@ -179,8 +153,8 @@ public class QueryBuilder : StatementBuilder {
             return @"$column_name $dir";
         }
 
-        public static string all_to_string(OrderingTerm[] terms) {
-            if (terms.length == 0) return "";
+        public static string all_to_string(OrderingTerm[]? terms) {
+            if (terms == null || terms.length == 0) return "";
             string res = "ORDER BY "+terms[0].to_string();
             for (int i = 1; i < terms.length; i++) {
                 res += @", $(terms[i])";
diff --git a/qlite/src/row.vala b/qlite/src/row.vala
index 96762be3..8854656f 100644
--- a/qlite/src/row.vala
+++ b/qlite/src/row.vala
@@ -4,7 +4,7 @@ using Sqlite;
 namespace Qlite {
 
 public class Row {
-    private Map<string, string> text_map = new HashMap<string, string>();
+    private Map<string, string?> text_map = new HashMap<string, string?>();
     private Map<string, long> int_map = new HashMap<string, long>();
     private Map<string, double?> real_map = new HashMap<string, double?>();
 
@@ -43,8 +43,8 @@ public class Row {
         return int_map.has_key(field);
     }
 
-    public double get_real(string field) {
-        return real_map[field];
+    public double get_real(string field, double def = 0) {
+        return real_map[field] ?? def;
     }
 
     public bool has_real(string field) {
@@ -71,11 +71,21 @@ public class RowIterator {
         }
     }
 
-    public Row? next_value() throws DatabaseError {
+    public bool next() {
         int r = stmt.step();
-        if (r == Sqlite.ROW) return new Row(stmt);
-        if (r == Sqlite.DONE) return null;
-        throw new DatabaseError.EXEC_ERROR(@"SQLite error: $(db.errcode()) - $(db.errmsg())");
+        if (r == Sqlite.ROW) return true;
+        if (r == Sqlite.DONE) return false;
+        print(@"SQLite error: $(db.errcode()) - $(db.errmsg())\n");
+        return false;
+    }
+
+    public Row get() {
+        return new Row(stmt);
+    }
+
+    public Row? get_next() {
+        if (next()) return get();
+        return null;
     }
 }
 
@@ -91,8 +101,13 @@ public class RowOption {
     }
 
     public T get<T>(Column<T> field, T def = null) {
-        if (inner == null || field.is_null(inner)) return def;
-        return field[inner];
+        if (inner == null || field.is_null((!)inner)) return def;
+        return field[(!)inner];
+    }
+
+    internal long get_integer(string field, long def = 0) {
+        if (inner == null || !((!)inner).has_integer(field)) return def;
+        return ((!)inner).get_integer(field);
     }
 }
 
diff --git a/qlite/src/statement_builder.vala b/qlite/src/statement_builder.vala
index 11efb0de..6097a9cc 100644
--- a/qlite/src/statement_builder.vala
+++ b/qlite/src/statement_builder.vala
@@ -11,25 +11,32 @@ public abstract class StatementBuilder {
 
     internal abstract Statement prepare() throws DatabaseError;
 
-    internal class Field<T> {
+    internal abstract class AbstractField<T> {
         public T value;
         public Column<T>? column;
 
-        public Field(Column<T>? column, T value) {
-            this.column = column;
+        public AbstractField(T value) {
             this.value = value;
         }
 
-        internal virtual void bind(Statement stmt, int index) {
-            if (column != null) {
-                column.bind(stmt, index, value);
-            }
+        internal abstract void bind(Statement stmt, int index);
+    }
+
+    internal class Field<T> : AbstractField<T> {
+        public Field(Column<T> column, T value) {
+            base(value);
+            this.column = column;
+        }
+
+        internal override void bind(Statement stmt, int index) {
+            ((!)column).bind(stmt, index, value);
         }
     }
 
-    internal class NullField<T> : Field<T> {
-        public NullField(Column<T>? column) {
-            base(column, null);
+    internal class NullField<T> : AbstractField<T> {
+        public NullField(Column<T> column) {
+            base(null);
+            this.column = column;
         }
 
         internal override void bind(Statement stmt, int index) {
@@ -37,9 +44,9 @@ public abstract class StatementBuilder {
         }
     }
 
-    internal class StringField : Field<string> {
+    internal class StringField : AbstractField<string> {
         public StringField(string value) {
-            base(null, value);
+            base(value);
         }
 
         internal override void bind(Statement stmt, int index) {
diff --git a/qlite/src/table.vala b/qlite/src/table.vala
index 2a80c9a5..b4f2fee7 100644
--- a/qlite/src/table.vala
+++ b/qlite/src/table.vala
@@ -5,22 +5,21 @@ namespace Qlite {
 public class Table {
     protected Database db;
     public string name { get; private set; }
-    protected Column[] columns;
-    private string constraints;
+    protected Column[]? columns;
+    private string constraints = "";
 
     public Table(Database db, string name) {
         this.db = db;
         this.name = name;
     }
 
-    public void init(Column[] columns, string? constraints = null) {
+    public void init(Column[] columns, string constraints = "") {
         this.columns = columns;
         this.constraints = constraints;
     }
 
     public void unique(Column[] columns, string? on_conflict = null) {
-        if (constraints == null) constraints = ""; else constraints += ", ";
-        constraints += "UNIQUE (";
+        constraints += ", UNIQUE (";
         bool first = true;
         foreach (Column c in columns) {
             if (!first) constraints += ", ";
@@ -29,7 +28,7 @@ public class Table {
         }
         constraints += ")";
         if (on_conflict != null) {
-            constraints += "ON CONFLICT " + on_conflict;
+            constraints += "ON CONFLICT " + (!)on_conflict;
         }
     }
 
@@ -80,10 +79,7 @@ public class Table {
                 sql += @"$(i > 0 ? "," : "") $c";
             }
         }
-        if (constraints != null) {
-            sql += ", " + constraints;
-        }
-        sql += ")";
+        sql += @"$constraints)";
         db.exec(sql);
     }
 
@@ -98,10 +94,10 @@ public class Table {
 
     public void delete_columns_for_version(long old_version, long new_version) throws DatabaseError {
         bool column_deletion_required = false;
-        string column_list = null;
+        string column_list = "";
         foreach (Column c in columns) {
             if (c.min_version <= new_version && c.max_version >= new_version) {
-                if (column_list == null) {
+                if (column_list == "") {
                     column_list = c.name;
                 } else {
                     column_list += ", " + c.name;
diff --git a/qlite/src/update_builder.vala b/qlite/src/update_builder.vala
index 6aad2aa1..139009c5 100644
--- a/qlite/src/update_builder.vala
+++ b/qlite/src/update_builder.vala
@@ -5,18 +5,18 @@ namespace Qlite {
 public class UpdateBuilder : StatementBuilder {
 
     // UPDATE [OR ...]
-    private string or_val;
+    private string? or_val;
 
     // [...]
-    private Table table;
+    private Table? table;
     private string table_name;
 
     // SET [...]
-    private StatementBuilder.Field[] fields;
+    private StatementBuilder.AbstractField[] fields = {};
 
     // WHERE [...]
-    private string selection;
-    private StatementBuilder.Field[] selection_args;
+    private string selection = "1";
+    private StatementBuilder.AbstractField[] selection_args = {};
 
     internal UpdateBuilder(Database db, Table table) {
         base(db);
@@ -35,59 +35,28 @@ public class UpdateBuilder : StatementBuilder {
     }
 
     public UpdateBuilder set<T>(Column<T> column, T value) {
-        if (fields == null) {
-            fields = { new StatementBuilder.Field<T>(column, value) };
-        } else {
-            StatementBuilder.Field[] fields_new = new StatementBuilder.Field[fields.length+1];
-            for (int i = 0; i < fields.length; i++) {
-                fields_new[i] = fields[i];
-            }
-            fields_new[fields.length] = new Field<T>(column, value);
-            fields = fields_new;
-        }
+        fields += new Field<T>(column, value);
         return this;
     }
 
     public UpdateBuilder set_null<T>(Column<T> column) throws DatabaseError {
         if (column.not_null) throw new DatabaseError.ILLEGAL_QUERY(@"Can't set non-null column $(column.name) to null");
-        if (fields == null) {
-            fields = { new NullField<T>(column) };
-        } else {
-            StatementBuilder.Field[] fields_new = new StatementBuilder.Field[fields.length+1];
-            for (int i = 0; i < fields.length; i++) {
-                fields_new[i] = fields[i];
-            }
-            fields_new[fields.length] = new NullField<T>(column);
-            fields = fields_new;
-        }
+        fields += new NullField<T>(column);
         return this;
     }
 
-    public UpdateBuilder where(string selection, string[]? selection_args = null) throws DatabaseError {
-        if (this.selection != null) throw new DatabaseError.ILLEGAL_QUERY("selection was already done, but where() was called.");
+    public UpdateBuilder where(string selection, string[] selection_args = {}) throws DatabaseError {
+        if (this.selection != "1") throw new DatabaseError.ILLEGAL_QUERY("selection was already done, but where() was called.");
         this.selection = selection;
-        if (selection_args != null) {
-            this.selection_args = new StatementBuilder.Field[selection_args.length];
-            for (int i = 0; i < selection_args.length; i++) {
-                this.selection_args[i] = new StatementBuilder.StringField(selection_args[i]);
-            }
+        foreach (string arg in selection_args) {
+            this.selection_args += new StatementBuilder.StringField(arg);
         }
         return this;
     }
 
     public UpdateBuilder with<T>(Column<T> column, string comp, T value) {
-        if (selection == null) {
-            selection = @"$(column.name) $comp ?";
-            selection_args = { new StatementBuilder.Field<T>(column, value) };
-        } else {
-            selection = @"($selection) AND $(column.name) $comp ?";
-            StatementBuilder.Field[] selection_args_new = new StatementBuilder.Field[selection_args.length+1];
-            for (int i = 0; i < selection_args.length; i++) {
-                selection_args_new[i] = selection_args[i];
-            }
-            selection_args_new[selection_args.length] = new Field<T>(column, value);
-            selection_args = selection_args_new;
-        }
+        selection_args += new Field<T>(column, value);
+        selection = @"($selection) AND $(column.name) $comp ?";
         return this;
     }
 
@@ -103,13 +72,13 @@ public class UpdateBuilder : StatementBuilder {
 
     internal override Statement prepare() throws DatabaseError {
         string sql = "UPDATE";
-        if (or_val != null) sql += @" OR $or_val";
+        if (or_val != null) sql += @" OR $((!)or_val)";
         sql += @" $table_name SET ";
         for (int i = 0; i < fields.length; i++) {
             if (i != 0) {
                 sql += ", ";
             }
-            sql += @"$(fields[i].column.name) = ?";
+            sql += @"$(((!)fields[i].column).name) = ?";
         }
         sql += @" WHERE $selection";
         Statement stmt = db.prepare(sql);
@@ -123,7 +92,7 @@ public class UpdateBuilder : StatementBuilder {
     }
 
     public void perform() throws DatabaseError {
-        if (fields == null || fields.length == 0) return;
+        if (fields.length == 0) return;
         if (prepare().step() != DONE) {
             throw new DatabaseError.EXEC_ERROR(@"SQLite error: $(db.errcode()) - $(db.errmsg())");
         }