net.sf.basedb.core.query
Class Selects

java.lang.Object
  net.sf.basedb.core.query.Selects

public class Selects
extends Object

A factory class to create select expressions.

Version:

2.0

Author:

Nicklas

Last modified

$Date: 2009-06-23 11:30:37 +0200 (Tue, 23 Jun 2009) $

Field Summary

static Pattern

ALIAS_REGEXP An alias can only contain the characters a-z, A-Z or 0-9.

Constructor Summary

Selects()

Method Summary

static Select	expression(Expression e1, String alias) Same as expression(e1, alias, false).
static Select	expression(Expression e1, String alias, boolean useInDistinctCount) Create a selection from an expression, optionally giving it an alias.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

ALIAS_REGEXP

public static final Pattern ALIAS_REGEXP

An alias can only contain the characters a-z, A-Z or 0-9.

Constructor Detail

Selects

public Selects()

Method Detail

expression

public static final Select expression(Expression e1,
                                      String alias)
                               throws InvalidDataException

Same as expression(e1, alias, false).

Parameters:

e1 - The expression to select. Null is not allowed

alias - The alias to give the expression. Only characters a-z, A-Z and 0-9 are allowed. Null is allowed.

Returns:

A selection query element

Throws:

InvalidDataException - If the required parameter is null or if illegal characters is used in alias

See Also:

expression(Expression, String, boolean)

expression

public static final Select expression(Expression e1,
                                      String alias,
                                      boolean useInDistinctCount)
                               throws InvalidDataException

Create a selection from an expression, optionally giving it an alias. The alias can be used when getting the result to find the column index. See SqlResultIterator.getIndex(String).

SELECT <expression> AS <alias>
FROM ...
        

The useInDistinctCount parameter affects the Query.count(DbControl) method, if the Query.setDistinct(boolean) has been set to true. In this case only expressions which has been created for use with the distinct function are used in the selection list:

SELECT COUNT(DISTINCT <expression>)
FROM ...
        

Parameters:

e1 - The expression to select

alias - The alias to give the expression

useInDistinctCount - If the expression should be used when counting distinct values

Returns:

A selection query element

Throws:

InvalidDataException - If the expression is null or if the alias contains invalid characters