寻求MySQL与HSQLDB通用的UUID获取SQL语句方案

Ah, the classic multi-database syntax headache! You're right that MySQL lets you run SELECT UUID(); directly, while HSQLDB requires a FROM clause (or workarounds like VALUES/CALL). Here's how to write a query that works seamlessly in both:

The Simplest Solution: Use the DUAL Dummy Table #

Both databases support the DUAL virtual table, which is perfect for queries that don't need a real underlying table:

SELECT UUID() FROM DUAL;

• MySQL: DUAL is a built-in dummy table, so this behaves exactly like running SELECT UUID(); directly.
• HSQLDB: DUAL is recognized as a valid virtual table, satisfying its requirement for a FROM clause while properly executing the UUID() function.

Alternative: Use a VALUES Subquery #

If you prefer avoiding DUAL, the VALUES subquery you already tested works in both databases too:

SELECT UUID() FROM (VALUES(0)) AS t;

MySQL handles this subquery as a valid data source, and HSQLDB already accepts this syntax as you've verified.

Quick Note #

Just ensure HSQLDB's UUID function is enabled (you mentioned this is already confirmed, which is great—this feature is enabled by default, but it's worth double-checking if you run into unexpected issues).

内容的提问来源于stack exchange，提问作者user2083529