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

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.DBAliasExpr
All Implemented Interfaces:
Serializable, ColumnExpr

public class DBAliasExpr
extends DBColumnExpr

This class allows column renaming in SQL.

There is no need to explicitly create instances of this class.
Instead use DBColumnExpr.as(String)

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
DBAliasExpr(DBColumnExpr expr, String alias)
          Constructs a DBAliasExpr object combine the DBColumnExpr object with the alias name.
 
Method Summary
 void addReferencedColumns(Set<DBColumn> list)
          Internal function to obtain all DBColumnExpr-objects used by this expression.
 void addSQL(StringBuilder buf, long context)
          Creates the SQL-Command adds the alias name to the SQL-Command.
 Element addXml(Element parent, long flags)
          This function set the alias name to the XML tag.
 boolean equals(Object other)
          Overrides the equals method
 DBDatabase getDatabase()
          Returns the current DBDatabase object.
 DataType getDataType()
          Returns the data type of the DBColumnExpr object.
 DBColumnExpr getExpr()
          This helper function returns the underlying column expression.
 String getName()
          This helper function returns the alias name.
 DBColumn getUpdateColumn()
          Returns the DBColunm object.
 boolean isAggregate()
          Always returns false since an alias expression cannot be an aggregate.
 String toString()
          Overrides the toString method.
 
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, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

DBAliasExpr

public DBAliasExpr(DBColumnExpr expr,
                   String alias)
Constructs a DBAliasExpr object combine the DBColumnExpr object with the alias name.

Parameters:
expr - an DBColumnExpr object, one column
alias - the alias name of the column
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 of the DBColumnExpr object.

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

getName

public String getName()
This helper function returns the alias name.

Specified by:
getName in interface ColumnExpr
Specified by:
getName in class DBColumnExpr
Returns:
the alias name

getExpr

public DBColumnExpr getExpr()
This helper function returns the underlying column expression.

Returns:
the underlying column expression

addXml

public Element addXml(Element parent,
                      long flags)
This function set the alias name to the XML tag.

Specified by:
addXml in class DBColumnExpr
Parameters:
parent - the parent element to which to append the column description
flags - currently not used
Returns:
the XML tag (with the alias name)

getUpdateColumn

public DBColumn getUpdateColumn()
Returns the DBColunm object.

Specified by:
getUpdateColumn in class DBColumnExpr
Returns:
the DBColunm object

isAggregate

public boolean isAggregate()
Always returns false since an alias expression cannot be an aggregate.

Specified by:
isAggregate in class DBColumnExpr
Returns:
false

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 buf,
                   long context)
Creates the SQL-Command adds the alias name to the SQL-Command.

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

equals

public boolean equals(Object other)
Overrides the equals method

Overrides:
equals in class Object
Returns:
true if alias name and expression match

toString

public String toString()
Overrides the toString method.

Overrides:
toString in class Object
Returns:
the alias name


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