From EJBQLParser.jjt:

void ComparisonExpression() #void :
{}
{
 (
 StringValue()
 (
 <EQ> { jjtThis.opp="="; } |
 <NE> { jjtThis.opp="<>"; }
 )
 StringExpression()
 ) #StringComparison
|
 (
 BooleanValue()
 [
 (
 <EQ> { jjtThis.opp="="; } |
 <NE> { jjtThis.opp="<>"; }
 ) BooleanExpression()
 ]
 ) #BooleanComparison
|
 (
 DatetimeValue()
 (
 <EQ> { jjtThis.opp="="; } |
 <GT> { jjtThis.opp=">"; } |
 <LT> { jjtThis.opp="<"; } |
 <NE> { jjtThis.opp="<>"; }
 )
 DatetimeExpression()
 ) #DatetimeComparison
|
 (
 EntityBeanValue()
 (
 <EQ> { jjtThis.opp="="; } |
 <NE> { jjtThis.opp="<>"; }
 )
 EntityBeanExpression()
 ) #EntityComparison
|
 LOOKAHEAD(ArithmeticValue() ( <EQ> | <GT> | <GE> | <LT> | <LE> | <NE> ) )
 (
 ArithmeticValue()
 (
 <EQ> { jjtThis.opp="="; } |
 <GT> { jjtThis.opp=">"; } |
 <GE> { jjtThis.opp=">="; } |
 <LT> { jjtThis.opp="<"; } |
 <LE> { jjtThis.opp="<="; } |
 <NE> { jjtThis.opp="<>"; }
 )
 SingleValueDesignator()
 ) #ArithmeticComparison
|
 BetweenExpression()
}