Overview  Package   Class  Use  Deprecated  Index
Home >> All >> javatools >> [ db overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

---

javatools.db
Class DbFalseExpr  

java.lang.Object
  javatools.db.DbExpr
      javatools.db.DbCriterion
          javatools.db.DbFalseExpr

All Implemented Interfaces:

DbTableUser

---

public class DbFalseExpr

extends DbCriterion

An expression that always evaluates to false. If not optimised away by DbTrueExpr, it will probably result in "0 = 1" in the SQL.

The use of false expressions makes it very convenient for dynamically generated queries...

 DbExpr e = db.falseExpr();
 if (name != null) {
  e = e.or(table.getColumn("NAME")).equals(name));
 }
 if (age != null) {
  e = e.or(table.getColumn("AGE")).equals(age));
 }
 

This gets converted to...

 (0 = 1) OR ( NAME = ? ) OR ( AGE = ? )
 

and then DbOrExpr optimises this to...

 ( NAME = ? ) OR ( AGE = ? )
 

Version:

0.7

---

Field Summary

 

Fields inherited from class javatools.db.DbCriterion

c1, c2, op

 

Fields inherited from class javatools.db.DbExpr

db

 

Constructor Summary

DbFalseExpr(DbDatabase db)           Builds a new false expression.

 

Methods inherited from class javatools.db.DbCriterion

getQueryString, setSqlValues, usesTables

 

Methods inherited from class javatools.db.DbExpr

and, containsAllStrings, containsAllStrings, count, dateTrunc, equal, getString, greaterThan, greaterThanOrEqual, in, in, isNotNull, isNull, lessThan, lessThanOrEqual, like, lower, max, min, notEqual, notIn, notIn, or, setSqlValue, upper, usesTables

 

Methods inherited from class java.lang.Object

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

 

Constructor Detail

DbFalseExpr

public DbFalseExpr(DbDatabase db)

Builds a new false expression.

---

Overview  Package   Class  Use  Deprecated  Index
Home >> All >> javatools >> [ db overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

---