"正确"在HSQLDB 2.0.0-rc8中选择下一个序列值的方法 [英] "correct" way to select next sequence value in HSQLDB 2.0.0-rc8

问题描述

假设我有一个序列，名为TEST_SEQ
，那么选择下一个值的正确方法是什么？
这不起作用：

 为TEST_SEQ选择下一个值 

可能是因为它期望有一个FROM子句。
在hibernate中查看HSQLDialect.getSequenceNextValString（）我看到这个：

 select next value for+ sequenceName + from dual_+ sequenceName  

在我的情况下会导致类似的结果：

 从dual_TEST_SEQ中为TEST_SEQ选择下一个值 

为2.0.0-RC8工作（我只假设这在2.0版以前的版本 - 未经验证）
我遇到了一个解决方案，涉及创建一个简单的表，称为DUAL，在这种情况下，这将工作（oracle风格）：

 从DUAL选择下一个TEST_SEQ值 

但是hsqldb并没有附带这个表格，我不知道如何让hibernate在第一次启动时生成这样的表格。

我认为必须有一种方法来获得开箱即用的下一个值，并且即时忽略它。
的任何想法？

解决方案

假设我有一个序列，称为TEST_SEQ什么是选择下一个值的正确方法是什么？

虽然 documentation 表示：

序列的下一个值可以包含在SELECT，INSERT和UPDATE语句如下例所示：

  SELECT [...，] NEXT VALUE FOR< sequencename> [，...] FROM< tablename>; 
  

正确的方式（因为更简单，因为不涉及表像HSQLDB不具备的DUAL DUAL表一样）：

 调用[sequence_name]的下一个值; 
  

这出现在 1.7.2 ，这实际上Hibernate是如何处理最近的 HSQLDialect Hibernate Core版本（请参阅 HHH-2839 ）。

事实上，这就是我在 HSQLDialect 中看到的 hibernate-core- 3.3.0.SP1.jar ：

  public String getSequenceNextValString（String sequenceName）{
返回call next value for+ sequenceName; 
 
 
 
 
 
 $ b 
所以我的建议是：升级到更新版本的Hibernate，你很可能使用Hibernate Core 3.2.5或更高版本。
 
suppose i have a sequence, called TEST_SEQ
what would be the correct way of selecting its next value ?
this does not work:
select next value for TEST_SEQ
probably because it expects a "FROM" clause.
looking at HSQLDialect.getSequenceNextValString() in hibernate i see this:
"select next value for " + sequenceName + " from dual_" + sequenceName
which in my case would result in something like:
select next value for TEST_SEQ from dual_TEST_SEQ
which does not work for 2.0.0-rc8 (i only assume this works in pre-2.0 versions - havent verified)
I've come across a solution that involves creating a simple table with 1 row called DUAL, in which case this will work (oracle style):
select next value for TEST_SEQ from DUAL
but hsqldb does not come with this table out of the box, and im not sure how i can get hibernate to generate such a table on "first boot".

Im thinking there has to be a way to get the next value for a sequence out of the box and im just missing it.
any ideas ?
解决方案

  
suppose i have a sequence, called TEST_SEQ what would be the correct way of selecting its next value ?
While the documentation says:

  
The next value for a sequence can be included in SELECT, INSERT and UPDATE statements as in the following example:
SELECT [...,] NEXT VALUE FOR <sequencename> [, ...] FROM <tablename>;

the "correct" way (because simpler, because not involving a table like a dumb DUAL table that HSQLDB doesn't have) would be:
call NEXT VALUE FOR [sequence_name];
This appeared in 1.7.2 and this his actually how Hibernate handles sequences in the HSQLDialect of "recent" versions of  Hibernate Core (see HHH-2839). 

And indeed, this is what I see in the HSQLDialect of hibernate-core-3.3.0.SP1.jar:
public String getSequenceNextValString(String sequenceName) {
    return "call next value for " + sequenceName;
}
So my advice is: upgrade to a newer version of Hibernate, you are very likely using Hibernate Core 3.2.5 or prior.

                        
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