是否有办法从已删除的记录中获得键?

Question

我使用PostgreSQL将表单保存在三个表中，一个表用于名称和id，另一个表用于填充字段，第三个表用于存储字段的值。

private static final String REMOVE_FORM = "DELETE FROM forms WHERE name = ?";
private PreparedStatement removeFormQuery;
public boolean connect() throws SQLException{
this.connection = DriverManager.getConnection(URL);
this.removeFormQuery = this.connection.prepareStatement(REMOVE_FORM);
}
public void close() throws SQLException {
if(null != this.connection) {
this.connection.close();
}
if(null != this.removeFormQuery) {
this.removeFormQuery.close();
}
}

private void removeForm(String form) {
try {
removeFormQuery.setString(1, form);
int execute = removeFormQuery.executeUpdate();
System.out.println(execute);
ResultSet generatedKeys = removeFormQuery.getGeneratedKeys();
while (generatedKeys.next()) {
int anInt1 = generatedKeys.getInt("id");
removeFieldQuery.setInt(1, anInt1);
if (removeFieldQuery.execute())
System.out.println("remove field failed");
else
System.out.println("remove field success");
ResultSet generatedFieldsKeys = removeFieldQuery.getGeneratedKeys();
while (generatedFieldsKeys.next()) {
int anInt = generatedFieldsKeys.getInt("id");
removeListItemQuery.setInt(1, anInt);
if (removeListItemQuery.execute())
System.out.println("remove listItem failed");
else
System.out.println("remove listItem success");
}
}
} catch (SQLException e) {
e.printStackTrace();
}
}

代码不生成键删除查询执行后，我错过了什么?

Answer 1

当你没有告诉我们你正在运行什么查询时，如果它们是deletes，那么你就不会期望任何生成的键

From Javadoc forStatement.getGeneratedKeys():

* Retrieves any auto-generated keys created as a result of executing this
* Statement object. If this Statement object did
* not generate any keys, an empty ResultSet
* object is returned.

当你插入一个表，创建一个需要主键的新行时，键可能会自动生成，但是当你删除一个行时，不会生成键。