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javatools.db
Class DbTrueExpr  

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

All Implemented Interfaces:

DbTableUser

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public class DbTrueExpr

extends DbCriterion

An expression that always evaluates to true. If not optimised away but DbAndExpr, this will probably result in "0 = 0" in the SQL.

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

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

This gets converted to...

 (0 = 0) AND ( NAME = ? ) AND ( AGE = ? )
 

and then DbAndExpr optimises this to...

 ( NAME = ? ) AND ( AGE = ? )
 

Version:

0.7

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Field Summary

 

Fields inherited from class javatools.db.DbCriterion

c1, c2, op

 

Fields inherited from class javatools.db.DbExpr

db

 

Constructor Summary

DbTrueExpr(DbDatabase db)           Creates a new DbTrueExpr 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

DbTrueExpr

public DbTrueExpr(DbDatabase db)

Creates a new DbTrueExpr expression.

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