Class ColumnSelect<T>
- All Implemented Interfaces:
- Serializable,- Query,- Select<T>
public class ColumnSelect<T> extends FluentSelect<T>
A helper builder for queries selecting individual properties based on the root object.
It can be used to select properties of the object itself, properties of related entities or some function calls (including aggregate functions).
Usage examples:
 
      // select list of names:
      List<String> names = ObjectSelect.columnQuery(Artist.class, Artist.ARTIST_NAME).select(context);
      // select count:
      long count = ObjectSelect.columnQuery(Artist.class, Property.COUNT).selectOne();
      // select only required properties of an entity:
      List<Object[]> data = ObjectSelect.columnQuery(Artist.class, Artist.ARTIST_NAME, Artist.DATE_OF_BIRTH)
                                  .where(Artist.ARTIST_NAME.like("Picasso%))
                                  .select(context);
 
 
 
 Note: this class can't be instantiated directly. Use ObjectSelect.
- Since:
- 4.0
- See Also:
- ObjectSelect.columnQuery(Class, Property), Serialized Form
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Field SummaryFields inherited from class org.apache.cayenne.query.FluentSelectcacheGroup, cacheStrategy, dbEntityName, entityName, entityType, limit, offset, orderings, pageSize, prefetches, statementFetchSize, whereFields inherited from class org.apache.cayenne.query.IndirectQuerydataMap, lastResolver, name, replacementQuery
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Constructor SummaryConstructors Modifier Constructor Description protectedColumnSelect()protectedColumnSelect(ObjectSelect<T> select)Copy constructor to convert ObjectSelect to ColumnSelect
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Method SummaryModifier and Type Method Description ColumnSelect<T>and(Collection<Expression> expressions)AND's provided expressions to the existing WHERE or HAVING clause expression.ColumnSelect<T>and(Expression... expressions)AND's provided expressions to the existing WHERE clause expression.ColumnSelect<Object[]>avg(Property<?> property)Select average value of propertyColumnSelect<T>cacheGroup(String cacheGroup)ColumnSelect<T>cacheStrategy(QueryCacheStrategy strategy)ColumnSelect<T>cacheStrategy(QueryCacheStrategy strategy, String cacheGroup)protected <E> ColumnSelect<E>column(Property<E> property)ColumnSelect<Object[]>columns(Collection<Property<?>> properties)Add properties to select.ColumnSelect<Object[]>columns(Property<?> firstProperty, Property<?>... otherProperties)Add properties to select.ColumnSelect<Object[]>count()Shortcut forcolumns(Property, Property[])columns}(Property.COUNT)ColumnSelect<Object[]>count(Property<?> property)Select COUNT(property)protected QuerycreateReplacementQuery(EntityResolver resolver)Translates self to a SelectQuery.ColumnSelect<T>dbEntityName(String dbEntityName)Sets theDbEntityname to fetch without changing the return type of the query.ColumnSelect<T>distinct()Explicitly request distinct in query.ColumnSelect<T>entityName(String entityName)Sets theObjEntityname to fetch without changing the return type of the query.ColumnSelect<T>entityType(Class<?> entityType)Sets the type of the entity to fetch without changing the return type of the query.Collection<Property<?>>getColumns()ExpressiongetHaving()Returns a HAVING clause Expression of this query.ColumnSelect<T>having(String expressionString, Object... parameters)Appends a having qualifier expression of this query, using provided expression String and an array of position parameters.ColumnSelect<T>having(Expression expression)Appends a having qualifier expression of this query.ColumnSelect<T>limit(int fetchLimit)Resets query fetch limit - a parameter that defines max number of objects that should be ever be fetched from the database.ColumnSelect<T>localCache()Instructs Cayenne to look for query results in the "local" cache when running the query.ColumnSelect<T>localCache(String cacheGroup)Instructs Cayenne to look for query results in the "local" cache when running the query.ColumnSelect<Object[]>max(Property<?> property)Select maximum value of propertyColumnSelect<Object[]>min(Property<?> property)Select minimum value of propertyColumnSelect<T>offset(int fetchOffset)Resets query fetch offset - a parameter that defines how many objects should be skipped when reading data from the database.ColumnSelect<T>or(Collection<Expression> expressions)OR's provided expressions to the existing WHERE or HAVING clause expression.ColumnSelect<T>or(Expression... expressions)OR's provided expressions to the existing WHERE clause expression.ColumnSelect<T>orderBy(String property)Add an ascending ordering on the given property.ColumnSelect<T>orderBy(String property, SortOrder sortOrder)Add an ordering on the given property.ColumnSelect<T>orderBy(Collection<Ordering> orderings)Adds a list of orderings to this query.ColumnSelect<T>orderBy(Ordering... orderings)Add one or more orderings to this query.ColumnSelect<T>pageSize(int pageSize)Resets query page size.ColumnSelect<T>prefetch(String path, int semantics)Merges a prefetch path with specified semantics into the query prefetch tree.ColumnSelect<T>prefetch(PrefetchTreeNode prefetch)Merges prefetch into the query prefetch tree.TselectFirst(ObjectContext context)Selects a single object using provided context.ColumnSelect<T>sharedCache()Instructs Cayenne to look for query results in the "shared" cache when running the query.ColumnSelect<T>sharedCache(String cacheGroup)Instructs Cayenne to look for query results in the "shared" cache when running the query.ColumnSelect<T>statementFetchSize(int size)Sets fetch size of the PreparedStatement generated for this query.<E extends Number>
 ColumnSelect<Object[]>sum(Property<E> property)Select sum of valuesColumnSelect<T>suppressDistinct()Explicitly suppress distinct in query.ColumnSelect<T>where(String expressionString, Object... parameters)Appends a qualifier expression of this query, using provided expression String and an array of position parameters.ColumnSelect<T>where(Expression expression)Appends a qualifier expression of this query.Methods inherited from class org.apache.cayenne.query.FluentSelectbatchIterator, getCacheGroup, getCacheStrategy, getDbEntityName, getEntityName, getEntityType, getLimit, getOffset, getOrderings, getPageSize, getPrefetches, getStatementFetchSize, getWhere, iterate, iterator, select, selectOneMethods inherited from class org.apache.cayenne.query.IndirectQuerycreateSQLAction, getMetaData, getReplacementQuery, routeMethods inherited from class java.lang.Objectclone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, waitMethods inherited from interface org.apache.cayenne.query.QuerycreateSQLAction, getMetaData, route
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Constructor Details- 
ColumnSelectprotected ColumnSelect()
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ColumnSelectCopy constructor to convert ObjectSelect to ColumnSelect
 
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Method Details- 
createReplacementQueryDescription copied from class:FluentSelectTranslates self to a SelectQuery.- Overrides:
- createReplacementQueryin class- FluentSelect<T>
 
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entityTypeSets the type of the entity to fetch without changing the return type of the query.- Returns:
- this object
 
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entityNameSets theObjEntityname to fetch without changing the return type of the query. This form is most often used for generic entities that don't map to a distinct class.- Returns:
- this object
 
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dbEntityNameSets theDbEntityname to fetch without changing the return type of the query. This form is most often used for generic entities that don't map to a distinct class.- Returns:
- this object
 
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whereAppends a qualifier expression of this query. An equivalent toand(Expression...)that can be used a syntactic sugar.- Returns:
- this object
 
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whereAppends a qualifier expression of this query, using provided expression String and an array of position parameters. This is an equivalent to calling "and".- Returns:
- this object
 
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andAND's provided expressions to the existing WHERE clause expression.- Returns:
- this object
 
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orOR's provided expressions to the existing WHERE clause expression.- Returns:
- this object
 
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orderByAdd an ascending ordering on the given property. If there is already an ordering on this query then add this ordering with a lower priority.- Parameters:
- property- the property to sort on
- Returns:
- this object
 
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orderByAdd an ordering on the given property. If there is already an ordering on this query then add this ordering with a lower priority.- Parameters:
- property- the property to sort on
- sortOrder- the direction of the ordering
- Returns:
- this object
 
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orderByAdd one or more orderings to this query.- Returns:
- this object
 
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orderByAdds a list of orderings to this query.- Returns:
- this object
 
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prefetchMerges prefetch into the query prefetch tree.- Returns:
- this object
 
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prefetchMerges a prefetch path with specified semantics into the query prefetch tree.- Returns:
- this object
 
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limitResets query fetch limit - a parameter that defines max number of objects that should be ever be fetched from the database.
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offsetResets query fetch offset - a parameter that defines how many objects should be skipped when reading data from the database.
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pageSizeResets query page size. A non-negative page size enables query result pagination that saves memory and processing time for large lists if only parts of the result are ever going to be accessed.
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statementFetchSizeSets fetch size of the PreparedStatement generated for this query. Only non-negative values would change the default size.- See Also:
- Statement.setFetchSize(int)
 
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cacheStrategy
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cacheStrategy
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cacheGroup
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localCacheInstructs Cayenne to look for query results in the "local" cache when running the query. This is a short-hand notation for:query.cacheStrategy(QueryCacheStrategy.LOCAL_CACHE, cacheGroup); 
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localCacheInstructs Cayenne to look for query results in the "local" cache when running the query. This is a short-hand notation for:query.cacheStrategy(QueryCacheStrategy.LOCAL_CACHE); 
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columnsAdd properties to select. Can be any properties that can be resolved against root entity type (root entity properties, function call expressions, properties of relationships, etc). List<Object[]> columns = ObjectSelect.columnQuery(Artist.class, Artist.ARTIST_NAME) .columns(Artist.ARTIST_SALARY, Artist.DATE_OF_BIRTH) .select(context);- Parameters:
- firstProperty- first property
- otherProperties- array of properties to select
- See Also:
- column(Property),- columns(Collection)
 
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columnsAdd properties to select. Can be any properties that can be resolved against root entity type (root entity properties, function call expressions, properties of relationships, etc). - Parameters:
- properties- collection of properties, must contain at least one element
- See Also:
- columns(Property, Property[])
 
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column
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countShortcut for columns(Property, Property[])columns}(Property.COUNT)
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countSelect COUNT(property) Can return different result than COUNT(*) as it will count only non null values - See Also:
- count()
 
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minSelect minimum value of property - See Also:
- columns(Property, Property[])
 
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maxSelect maximum value of property - See Also:
- columns(Property, Property[])
 
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avgSelect average value of property - See Also:
- columns(Property, Property[])
 
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sumSelect sum of values - See Also:
- columns(Property, Property[])
 
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havingAppends a having qualifier expression of this query. An equivalent toand(Expression...)that can be used a syntactic sugar.- Returns:
- this object
 
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havingAppends a having qualifier expression of this query, using provided expression String and an array of position parameters. This is an equivalent to calling "and".- Returns:
- this object
 
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andAND's provided expressions to the existing WHERE or HAVING clause expression.- Returns:
- this object
 
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orOR's provided expressions to the existing WHERE or HAVING clause expression.- Returns:
- this object
 
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distinctExplicitly request distinct in query.
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suppressDistinctExplicitly suppress distinct in query.
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getColumns
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getHavingReturns a HAVING clause Expression of this query.
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selectFirstDescription copied from interface:SelectSelects a single object using provided context. The query itself can match any number of objects, but will return only the first one. It returns null if no objects were matched.If it matched more than one object, the first object from the list is returned. This makes 'selectFirst' different from Select.selectOne(ObjectContext), which would throw in this situation. 'selectFirst' is useful e.g. when the query is ordered and we only want to see the first object (e.g. "most recent news article"), etc.Selecting the first object via "Select.selectFirst(ObjectContext)" is more comprehensible than selecting via "ObjectContext.selectFirst(Select)", because implementations of "Select" set fetch size limit to one. 
 
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