问如何使用coalesce mysql

EN

 $query='update trac_patientprofiletable
    set name= COALESCE(name,"'.$name.'"),
        date_entered= COALESCE(date_entered,"'.$dateEntered.'"),
        patientdisease= COALESCE(patientdisease,"'.$_SESSION['input']['sPatientDisease'].'"),
        age= COALESCE(age,"'.$_SESSION['input']['sPatientAge'].'"),
        weight= COALESCE(weight,"'.$_SESSION['input']['sPatientWeight'].'"),
        maritalstatus= COALESCE(maritalstatus,"'.$_SESSION['input']['sPatientMaritalStatus'].'"),
        sex= COALESCE(sex,"'.$_SESSION['input']['sPatientSex'].'"),
        levelofeduca= COALESCE(levelofeduca,"'.$_SESSION['input']['sPatientEducationLevel'].'"),
        diagnosis= COALESCE(diagnosis,"'.$_SESSION['input']['sPatientDiagnosis'].'"),
        tbgroup= COALESCE(tbgroup,"'.$_SESSION['input']['sPatientTBgroup'].'"),
        cd4count= COALESCE(cd4count,"'.$_SESSION['input']['sPatientCD4Count'].'"),
        typeofart= COALESCE(typeofart,"'.$_SESSION['input']['sPatientARTRegimen'].'"),
        patientmobileno1= COALESCE(patientmobileno1,"'.$_SESSION['input']['sPatientPhoneNo'].'"),
        language= COALESCE(language,"'.$_SESSION['input']['sPatientCallLanguage'].'"),
        oiprophylaxis= COALESCE(oiprophylaxis,"'.$_SESSION['input']['sPatientOIProhylaxis'].'"),
        eligibleforart= COALESCE(eligibleforart,"'.$_SESSION['input']['sPatientEligibleART'].'"),
        dateartinitiated= COALESCE(dateartinitiated,"'.$_SESSION['input']['sPatientARTDate'].'")
    where patientid="'.$_SESSION['patientid'].'"';        
    $result=mysql_query($query) or die ("query error: ".mysql_error());