使用时如何区分数据库顺序 [英] How do I differentiate between databases when using e.g. sequence

问题描述

我刚刚开始使用 Liquibase ，并开始研究该问题以区分不同数据库的功能.

I just started using Liquibase and stumpled upon the problem to differentiate between the capabilities of different databases.

我们希望支持多个数据库(Oracle，MySQL，Derby-仅举三例).

We would like to support multiple databases (Oracle, MySQL, Derby - to name three).

所有功能都有不同.具体来说，Oracle支持sequences，而MySQL和Derby不支持.

The all have different capabilities. In specific Oracle supports sequences whereas MySQL and Derby do not.

当我让休眠生成DDL时，我可以选择不同的方言，当使用Oracle时它将考虑这些不同的功能并生成Sequencer，而在使用Derby或MySQL时使用普通表(用于ID生成).

When I let hibernate generate the DDL I can choose different dialects and it will consider these different capabilities and generate a Sequencer when using Oracle and use a plain table (for ID-generation) when using Derby or MySQL.

现在，我知道我可以通过在dbms属性中指定'oracle'来约束变更集.但是，我该如何为其他数据库做普通表解决方案呢? dbms似乎没有"not oracle"属性.

Now, I know I can constraint changesets by specifying 'oracle' in the dbms attribute. But then how can I do the plain table solution for the other databases? There does not seem to be a 'not oracle' attribute for dbms.

其他人如何处理呢? (我在liquibase页面或论坛上都找不到有关它的任何信息.)

How does anyone else handle this? (I could not find anything about it on the liquibase pages nor on the forum.)

推荐答案

尝试使用前提条件在changset上.支持布尔运算.

Try using a precondition on the changset. Boolean operations are supported.

例如

 <preConditions onFail="CONTINUE">
     <or>
         <dbms type="oracle" />
         <dbms type="mysql" />
     </or>
 </preConditions>

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