org.apache.empire.db.expr.column
Class DBCountExpr

java.lang.Object
  extended by org.apache.empire.db.DBObject
      extended by org.apache.empire.db.DBExpr
          extended by org.apache.empire.db.DBColumnExpr
              extended by org.apache.empire.db.expr.column.DBCountExpr
All Implemented Interfaces:
Serializable, ColumnExpr

public class DBCountExpr
extends DBColumnExpr

This class is used to add the "count" statement to the SQL-Command.

There is no need to explicitly create instances of this class.
Instead use or @link DBColumnExpr#count()

See Also:
Serialized Form

Field Summary
 
Fields inherited from class org.apache.empire.db.DBColumnExpr
attributes, beanPropertyName, DBCOLATTR_TITLE, DBCOLATTR_TYPE, options
 
Fields inherited from class org.apache.empire.db.DBExpr
CTX_ALIAS, CTX_ALL, CTX_DEFAULT, CTX_FULLNAME, CTX_NAME, CTX_NOPARENTHESES, CTX_VALUE
 
Constructor Summary
DBCountExpr(DBColumnExpr expr, boolean distinct)
          Constructs a DBCountExpr.
DBCountExpr(DBRowSet rowset)
          Constructs a DBCountExpr.
 
Method Summary
 void addReferencedColumns(Set<DBColumn> list)
          Internal function to obtain all DBColumnExpr-objects used by this expression.
 void addSQL(StringBuilder sql, long context)
          Creates the SQL-Command adds the String "count(*)" to the SQL-Command.
 Element addXml(Element parent, long flags)
          this adds the column description to the parent element
 DBDatabase getDatabase()
          Returns the current DBDatabase object.
 DataType getDataType()
          Returns the data type: DT_INTEGER.
 String getName()
          Returns the String "count".
 DBColumn getUpdateColumn()
          Returns null.
 boolean isAggregate()
          Returns true since the count function is an aggregate function.
 
Methods inherited from class org.apache.empire.db.DBColumnExpr
abs, append, as, as, asc, avg, cmp, coalesce, convertTo, convertTo, count, countDistinct, day, decode, decode, decode, decode, decode, decode, desc, detectDataType, divideBy, getAttribute, getBeanPropertyName, getControlType, getExprFromPhrase, getExprFromPhrase, getOptions, getSourceColumn, getTitle, in, indexOf, indexOf, indexOf, is, isBetween, isGreaterThan, isLessOrEqual, isMoreOrEqual, isNot, isNotBetween, isSmallerThan, length, like, like, likeLower, likeUpper, lower, max, min, minus, minus, month, multiplyWith, notIn, notLike, nvl, parenthesis, plus, plus, replace, reverse, round, setAttribute, setBeanPropertyName, setControlType, setOptions, setTitle, substring, substring, substring, substring, substring, substring, sum, toChar, toChar, trim, trimLeft, trimRight, trunc, upper, when, year
 
Methods inherited from class org.apache.empire.db.DBExpr
getObjectValue, getValueClass
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

DBCountExpr

public DBCountExpr(DBRowSet rowset)
Constructs a DBCountExpr.

Parameters:
rowset - the rowset

DBCountExpr

public DBCountExpr(DBColumnExpr expr,
                   boolean distinct)
Constructs a DBCountExpr.

Parameters:
expr - the column
distinct - set true for distinct count
Method Detail

getDatabase

public DBDatabase getDatabase()
Returns the current DBDatabase object.

Specified by:
getDatabase in class DBObject
Returns:
the current DBDatabase object

getDataType

public DataType getDataType()
Returns the data type: DT_INTEGER.

Specified by:
getDataType in interface ColumnExpr
Specified by:
getDataType in class DBColumnExpr
Returns:
the data type: DT_INTEGER
See Also:
DataType

getName

public String getName()
Returns the String "count".

Specified by:
getName in interface ColumnExpr
Specified by:
getName in class DBColumnExpr
Returns:
the String "count"

getUpdateColumn

public DBColumn getUpdateColumn()
Returns null.

Specified by:
getUpdateColumn in class DBColumnExpr
Returns:
null

isAggregate

public boolean isAggregate()
Returns true since the count function is an aggregate function.

Specified by:
isAggregate in class DBColumnExpr
Returns:
always true

addReferencedColumns

public void addReferencedColumns(Set<DBColumn> list)
Description copied from class: DBExpr
Internal function to obtain all DBColumnExpr-objects used by this expression.

Specified by:
addReferencedColumns in class DBExpr
Parameters:
list - list to which all used column expressions must be added
See Also:
DBExpr.addReferencedColumns(Set)

addSQL

public void addSQL(StringBuilder sql,
                   long context)
Creates the SQL-Command adds the String "count(*)" to the SQL-Command.

Specified by:
addSQL in class DBExpr
Parameters:
sql - the SQL-Command
context - the current SQL-Command context

addXml

public Element addXml(Element parent,
                      long flags)
this adds the column description to the parent element

Specified by:
addXml in class DBColumnExpr
Parameters:
parent - the parent element to which to append the column description
flags - currently not used
Returns:
the newly created child element


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