QtSql：绑定不会更改 SQLite 的查询

Question

我有以下代码应该将值绑定到 prepare 语句：

QSqlQuery query(db);
query.setForwardOnly(true);
query.prepare("SELECT Entry.* FROM Entry WHERE body LIKE ?;");
query.addBindValue(QVariant("%" + name + "%"));
query.exec();
tDebug("%s", query.executedQuery().toUtf8().data());

例如，如果 name 是 "thing"，那么查询应该执行语句 SELECT Entry.* FROM Entry WHERE body LIKE "%thing%"，但它执行 SELECT Entry.* FROM Entry WHERE body LIKE ?，几乎就像绑定值是忽略。命名占位符也有同样的问题。

Answer 1

我在等效示例上尝试了此操作，并适当地测试了 "prepare" 和 "exec" 的结果，这两个 return 都是布尔值。我测试了在 exec with:

之后这些值是有界的

  QList<QVariant> list = query.boundValues().values();
  for (int i = 0; i < list.size(); ++i)
    qDebug() << i << ": " << list.at(i).toString();

我用

测试了我得到了预期的结果

  while (query.next())
    qDebug()<<"result = "<<query.value(0);

确实，executedQuery 不包含有界值，但 Qt 中的注释对此有些含糊：

"If a prepared query with placeholders is executed on a DBMS that does not support it, the preparation of this query is emulated.The placeholders in the original query are replaced with their bound values to form a new query. This function returns the modified query. It is mostly useful for debugging purposes."

所以我假设对于 postgresql（我拥有的）和 SQLite，executedQuery 会 return 原始的占位符而不是有界值。

QtSql：绑定不会更改 SQLite 的查询

QtSql: binding doesn't change query with SQLite

c++

qt

qt5

qtsql