Java – count (*) (asterisk) on querydsl / MySQL?

The initial function is MySQL query, which lists all providers of all tags:

SELECT * FROM provider
  INNER JOIN provider_tag
  ON provider_tag.provider_id = provider.id AND provider_tag.tag_id in (1,2)
  GROUP BY (provider.id)
  HAVING COUNT(*) = 2

Converting to mysqlquery in querydsl is very simple

MysqLQuery query = new MysqLQuery(conn,dialect);

List<Integer> tagIds = ...;

query.from(provider)
    .innerJoin(provider_tag)
    .on(providerTag.providerId.eq(provider.id),providerTag.tagId.in(tagIds))
    .groupBy(provider.id)
    .having(???);

... except conditional

How to add count (*) to a query?

After Timo's first amendment proposal, edit:

So the query looks like this:

SearchResults<Tuple> result = query.from(provider)
    .innerJoin(providerTag)
    .on(providerTag.providerId.eq(provider.id),providerTag.tagId.in(tagIds))
    .groupBy(provider.id)
    .having(Wildcard.count.eq((long) tagIds.size()))
    .listResults(
        provider.id,provider.name);

However, if the result set is empty, it will cause sqlexception illegal operation on the empty result set

My other queries that return empty result sets will not cause exceptions, so I don't think I should catch exceptions, but there is a problem that needs to be fixed?

The generated MySQL works normally (returns 0 rows), so the problem does not exist

Edit 2:

The problem is in groupby() This appears to be valid if the correction shown in issue is applied

Solution

The querydsl equivalent of count (*) is wildcard count.