Check statement column count is consistent.

sqlite.go

@@ -350,7 +350,14 @@ func (c *Conn) Exists(query string, args ...interface{}) (bool, error) {
 		return false, err
 	}
 	defer s.Finalize()
-	return s.Next()
+	ok, err := s.Next()
+	if err != nil {
+		return false, err
+	}
+	if s.ColumnCount() == 0 {
+		return false, s.specificError("don't use Exists with query that returns no data such as %q", query)
+	}
+	return ok, nil
 }
 
 // OneValue is used with SELECT that returns only one row with only one column.
@@ -366,6 +373,9 @@ func (c *Conn) OneValue(query string, value interface{}, args ...interface{}) er
 	if err != nil {
 		return err
 	} else if !b {
+		if s.ColumnCount() == 0 {
+			return s.specificError("don't use OneValue with query that returns no data such as %q", query)
+		}
 		return io.EOF
 	}
 	return s.Scan(value)

stmt.go

@@ -163,6 +163,9 @@ func (s *Stmt) exec() error {
 		}
 		return s.error(rv, "Stmt.exec")
 	}
+	if s.ColumnCount() > 0 {
+		return s.specificError("don't use exec with anything that returns data such as %q", s.SQL())
+	}
 	return nil
 }
 
@@ -211,6 +214,9 @@ func (s *Stmt) Select(rowCallbackHandler func(s *Stmt) error, args ...interface{
 			return err
 		}
 	}
+	if s.ColumnCount() == 0 {
+		return s.specificError("don't use Select with query that returns no data such as %q", s.SQL())
+	}
 	for {
 		if ok, err := s.Next(); err != nil {
 			return err
@@ -233,6 +239,9 @@ func (s *Stmt) SelectOneRow(args ...interface{}) (bool, error) {
 	if ok, err := s.Next(); err != nil {
 		return false, err
 	} else if !ok {
+		if s.ColumnCount() == 0 {
+			return false, s.specificError("don't use SelectOneRow with query that returns no data such as %q", s.SQL())
+		}
 		return false, nil
 	}
 	return true, s.Scan(args...)

stmt_test.go

@@ -291,8 +291,14 @@ func TestStmtSelectWithInsert(t *testing.T) {
 	defer s.Finalize()
 
 	exists, err := s.SelectOneRow()
-	checkNoError(t, err, "SELECT error: %s")
-	assert.T(t, !exists, "no row expected")
+	assert.T(t, err != nil, "error expected")
+	//println(err.Error())
+	if serr, ok := err.(*StmtError); ok {
+		assert.Equal(t, ErrSpecific, serr.Code())
+	} else {
+		t.Errorf("Expected StmtError but got %s", reflect.TypeOf(err))
+	}
+	assert.T(t, !exists, "false expected")
 }
 
 func TestNamedBind(t *testing.T) {