如何将mysql别名列转换为别名列总和

Question

SELECT `id`,`setdate`,getfrname(careof) as rf_name,`patientid`,`name`,(getAmount(patientid)-discount) as gtotal,rfdiscount,getrfAmount(patientid) as rf_amt,rfpaidAmount(patientid) as rf_paid,(SELECT(rf_amt)-rfdiscount) as rf_payable,(SELECT(rf_payable)-SELECT(rf_paid)) as rf_due 
FROM `tbl_diagnosis` 
WHERE `rfpayable` = 0 and status = 1

//（SELECT（rf_payable）-SELECT（rf_paid））由于rf_due不起作用但是为什么??????????????????????????

Answer 1

尝试以下方式-因为您不能在其他计算字段中使用别名作为参考

SELECT `id`,`setdate`,getfrname(careof) as rf_name,`patientid`,`name`,
getAmount(patientid)-discount as gtotal,rfdiscount,
getrfAmount(patientid) as rf_amt,
rfpaidAmount(patientid) as rf_paid,
getrfAmount(patientid)-rfdiscount as rf_payable,
getrfAmount(patientid)-rfdiscount-rfpaidAmount(patientid) as rf_due 
FROM `tbl_diagnosis` 
WHERE `rfpayable` = 0 and status = 1