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POJava Criteria API: Select single column from one-to-many relationship table
 

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  1. POJava Criteria API: Select single column from one-to-many relationship table
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    <p>I am trying to select a single column from a related table. I have a table (Item) with many Values. I would like to select Value.valueString. </p> <p>Basically, the query is supposed to pass in a bunch of values and pull any ValueFields that contain those values. The SQL might look something like this:</p> <pre><code>select ItemValues.valueString from ItemEntity join StockItem on ItemEntity.stockItemId = StockItem.id join ItemValues on ItemEntity.id = ItemValues.itemId where StockItem.vendor = vendorId AND (ItemValues.valueString like '%test%' OR ItemValues.valueString like '%test2%'...); </code></pre> <p>Here is my code:</p> <pre><code> final CriteriaBuilder builder = this.entityManager.getCriteriaBuilder(); final CriteriaQuery&lt;String&gt; query = builder.createQuery(String.class); final Root&lt;ItemEntity&gt; root = query.from(ItemEntity.class); query.select(root.join("ItemValues").&lt;String&gt;get("ValueString")); final List&lt;Predicate&gt; filters = new LinkedList&lt;Predicate&gt;(); filters.add(builder.equal(root.join("StockItem").get("id"), vendorNumber)); final List&lt;Predicate&gt; filterNamesCriteria = new LinkedList&lt;Predicate&gt;(); if (filenames.length &gt; 0) { for (String fileName : filenames) { filterNamesCriteria.add(builder.like(root.join("ItemValues").&lt;String&gt;get("ValueString"), fileName)); } filters.add(builder.or(filterNamesCriteria.toArray(new Predicate[0]))); } query.where(filters.toArray(new Predicate[0])); final TypedQuery&lt;String&gt; resolvedQuery = this.entityManager.createQuery(query); return resolvedQuery.getResultList(); </code></pre> <p>I want the result to return a List of Strings (valueString column), but it's not returning anything.</p> <p>Am I doing something wrong? When I say "builder.createQuery(String.class)", is that correct?</p>
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    1. COYou need a Tuple: http://stackoverflow.com/questions/3842122/complex-queries-with-jpa-criteria-builder
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    2. COBut I'm only selecting one value. Isn't a tuple for multiselects?
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    3. CO@a.drew.b The OP doesn't need a tuple, the OP can achieve this using an IN operation. `select .. from ... where value IN :collection`. I could make an example but I don't feel like figuring out how the entities are mapped. OP please show how the entities are related (classes).
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Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

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