Using Jooq, I am trying to fetch from a table by id
first, if no matches found, then fetch by handle
again.
And I want all fields of the returned rows, not just one.
Field<?> firstMatch = DSL.select(Tables.MY_TABLE.fields())
.from(Tables.MY_TABLE.fields())
.where(Tables.MY_TABLE.ID.eq(id))
.asfield(); // This is wrong, because it supports only one field, but above we selected Tables.MY_TABLE.fields(), which is plural.
Field<?> secondMatch = DSL.select(Tables.MY_TABLE.fields())
.from(Tables.MY_TABLE.fields())
.where(Tables.MY_TABLE.HANDLE.eq(handle))
.asfield(); // Same as above.
dslContext.select(DSL.coalesce(firstMatch, secondMatch))
.fetchInto(MyClass.class);
Due to the mistake mentioned above in the code, the following error occurs:
Can only use single-column ResultProviderQuery as a field
I am wondering how to make firstMatch
and secondMatch
two lists of fields, instead of two fields?
I tried
Field<?>[] secondMatch = DSL.select(Tables.MY_TABLE.fields())
.from(Tables.MY_TABLE.fields())
.where(Tables.MY_TABLE.HANDLE.eq(handle))
.fields();
but the following error occurred in the line containing DSL.coalesce
Type interface org.jooq.Field is not supported in dialect DEFAULT
Thanks in advance!
This sounds much more like something you'd do with a simple OR
?
dslContext.selectFrom(MY_TABLE)
.where(MY_TABLE.ID.eq(id))
// The ne(id) part might not be required...
.or(MY_TABLE.ID.ne(id).and(MY_TABLE.HANDLE.eq(handle))
.fetchInto(MyClass.class);
If the two result sets should be completely exclusive, then you can do this:
dslContext.selectFrom(MY_TABLE)
.where(MY_TABLE.ID.eq(id))
.or(MY_TABLE.HANDLE.eq(handle).and(notExists(
selectFrom(MY_TABLE).where(MY_TABLE.ID.eq(id))
)))
.fetchInto(MyClass.class);
If on your database product, a query using OR
doesn't perform well, you can write an equivalent query with UNION ALL
, which might perform better.