Hql where is empty

You can, however, use in-memory database SqlLite and the likes and have Hibernate auto-create necessary schema for it. In theory you may be able to hack together a parser that would work without relying on metadata but I have a hardest time imagining what is it you're trying to do for this to be worth it.

Perhaps you can clarify? There has to be a better approach. HQL Query to check if size of collection is 0 or empty. The above query assumes that there are table rows where c. The parameter name 'type' may be a reserved word in SQL but it shouldn't matter since it is replaced before the query runs.

The javadoc for setParameter String, Object is explicit, saying that the Object value must be non-null. It's a shame that it doesn't throw an exception if a null is passed in, though. For example:. In order to refer to the Cat in other parts of the query, you will need to assign an alias.

This query assigns the alias cat to Cat instances, so you can use that alias later in the query. The as keyword is optional. You could also write:. Multiple classes can appear, resulting in a cartesian product or "cross" join. You may test the size of a collection with the special property size, or the special size function. In fact, the power of the query language is one of Hibernate's main strengths. The following example queries are similar to queries that have been used on recent projects.

Please note that most queries you will write will be much simpler than the following examples. The following query returns the order id, number of items, the given minimum total value and the total value of the order for all unpaid orders for a particular customer.

The results are ordered by total value. In determining the prices, it uses the current catalog. What a monster! Actually, in real life, I'm not very keen on subqueries, so my query was really more like this:. If the statusChanges collection was mapped as a list, instead of a set, the query would have been much simpler to write. The next query uses the MS SQL Server isNull function to return all the accounts and unpaid payments for the organization to which the current user belongs.

HQL now supports update , delete and insert If your database supports subselects, you can place a condition upon selection size in the where clause of your query:. As this solution cannot return a User with zero messages because of the inner join, the following form is also useful:. Collections are pageable by using the Query interface with a filter:.

Components can be used similarly to the simple value types that are used in HQL queries. They can appear in the select clause as follows:. Components can also be used in the where clause:. Another common use of components is in row value constructors. Here, we are generally referring to multi-valued comparisons, typically associated with components.

Consider an entity Person which defines a name component:. That is valid syntax although it is a little verbose. You can make this more concise by using row value constructor syntax:. It can also be useful to specify this in the select clause:. Using row value constructor syntax can also be beneficial when using subqueries that need to compare against multiple values:.

One thing to consider when deciding if you want to use this syntax, is that the query will be dependent upon the ordering of the component sub-properties in the metadata. Chapter Case Sensitivity The from clause Associations and joins Forms of join syntax Referring to identifier property The select clause Aggregate functions Polymorphic queries The where clause Expressions The order by clause The group by clause Subqueries