add db.QueryBoolean() shortcut method

db.go

@@ -364,6 +364,12 @@ func (db *DB) QueryRow(ctx context.Context, query string, args ...any) Row {
 	return db.Pool.QueryRow(ctx, query, args...)
 }
 
+// QueryBoolean executes a query that returns a single boolean value and returns it as a bool and an error.
+func (db *DB) QueryBoolean(ctx context.Context, query string, args ...any) (ok bool, err error) {
+	err = db.QueryRow(ctx, query, args...).Scan(&ok)
+	return
+}
+
 // Exec executes SQL. The query can be either a prepared statement name or an SQL string.
 // Arguments should be referenced positionally from the sql "query" string as $1, $2, etc.
 func (db *DB) Exec(ctx context.Context, query string, args ...any) (pgconn.CommandTag, error) {

desc/table.go

@@ -223,7 +223,7 @@ func (td *Table) ForeignKeyColumnNames() []string {
 
 // PrimaryKey returns the primary key's column of the
 // row definition and reports if there is one.
-func (td *Table) PrimaryKey() (*Column, bool) {
+func (td *Table) PrimaryKey() (*Column, bool) { // TODO: think of making it a static variable but keep the function somehow.
 	for _, c := range td.Columns {
 		if c.PrimaryKey {
 			return c, true

repository.go

@@ -51,6 +51,11 @@ func (repo *Repository[T]) QueryRow(ctx context.Context, query string, args ...a
 	return repo.db.QueryRow(ctx, query, args...)
 }
 
+// QueryBoolean executes a query that returns a single boolean value and returns it as a bool and an error.
+func (repo *Repository[T]) QueryBoolean(ctx context.Context, query string, args ...any) (bool, error) {
+	return repo.db.QueryBoolean(ctx, query, args...)
+}
+
 // Query executes a query that returns multiple rows and returns them as a Rows instance and an error.
 func (repo *Repository[T]) Query(ctx context.Context, query string, args ...any) (Rows, error) {
 	return repo.db.Query(ctx, query, args...)
@@ -182,6 +187,9 @@ func (repo *Repository[T]) InsertSingle(ctx context.Context, value T, idPtr any)
 	return repo.db.insertTableRecord(ctx, repo.td, desc.IndirectValue(value), idPtr, "", false) // delegate the insertion to repo.db.insertTableRecord and return its result
 }
 
+// DoNothing is a constant that can be used as the forceOnConflictExpr argument of Upsert/UpsertSingle to do nothing on conflict.
+const DoNothing = "DO NOTHING"
+
 // Upsert inserts or updates one or more values of type T into the database.
 func (repo *Repository[T]) Upsert(ctx context.Context, forceOnConflictExpr string, values ...T) error {
 	if repo.IsReadOnly() {