Question

我知道我可以做到：

IF( 2 = 2 AND 0 = 0, 1, 0 ) AS some_result, （当然输出1）

但是我在查询中有一些内部选择，例如：

(select ... ) as innerA,
(select ... ) as innerB,
(select ... ) as innerC,

然后我想做类似的事情：

IF( innerA, innerB, innerC ) AS my_result,（如果innerA则使用innerB，否则使用innerC）

但是我得到了错误Unknown column 'innerA' in 'field list'，因为它不是列，这是有道理的。

如何使用别名innerA，innerB和innerC生成my_result？

编辑：

为解释我的意思，以下是查询的相关部分：

(select t.id from transaction t where loan_id = l.id and status_id = 61) as chargeback_transaction_id,

(select t.`datestamp` from transaction t where loan_id = l.id and status_id = 61) as chargeback_transaction_id_date,

(select ls.`datestamp` from loan_status ls where loan_id = l.id and status_id = 16 and datestamp < chargeback_transaction_id_date ORDER BY datestamp DESC LIMIT 1) as loan_closed_transaction_id_date_before_the_chargeback_aka_status_16,

/* Get date of next status 9, after the first 16: */

(select ls.`datestamp` from loan_status ls where loan_id = l.id and status_id = 9 and datestamp > loan_closed_transaction_id_date_before_the_chargeback_aka_status_16 ORDER BY datestamp ASC LIMIT 1) as date_of_next_status_9_after_the_first_16,

(select ls2.`datestamp` from loan_status ls2 INNER JOIN client clj ON (clj.`client_id` = ls2.`loan_id`) where clj.client_id = '3378228' and loan_id != l.id and ls2.status_id = 9 and datestamp > loan_closed_transaction_id_date_before_the_chargeback_aka_status_16 and datestamp < date_of_next_status_9_after_the_first_16 LIMIT 1) as other_loan_datestamp,

IF( other_loan_datestamp, loan_closed_transaction_id_date_before_the_chargeback_aka_status_16, date_of_next_status_9_after_the_first_16 ) AS close_date_to_use,

我猜这最后一部分（IF( other_loan_datestamp,）完全没有意义，但是有没有办法用MySQL中的别名来做这样的'if else'逻辑？

注意：

other_loan_datestamp，loan_closed_transaction_id_date_before_the_chargeback_aka_status_16和date_of_next_status_9_after_the_first_16是类似于2018-05-25 12:31:16的日期

Answer 1

你有个主意

select if( i1.v, i2.v, i3.v ) as some_result
from (select 0 as v) i1, (select 2 as v) i2, (select 3 as v) i3

Answer 2

在这种情况下，您不能使用别名。不幸的是，您将不得不编写整个内容。另一种方法是将其包装在子查询中。

SELECT a.*
    , IF( a.other_loan_datestamp, a.loan_closed_transaction_id_date_before_the_chargeback_aka_status_16, a.date_of_next_status_9_after_the_first_16 ) AS close_date_to_use
FROM (
    (select t.id from transaction t where loan_id = l.id and status_id = 61) as chargeback_transaction_id,

    (select t.`datestamp` from transaction t where loan_id = l.id and status_id = 61) as chargeback_transaction_id_date,

    (select ls.`datestamp` from loan_status ls where loan_id = l.id and status_id = 16 and datestamp < chargeback_transaction_id_date ORDER BY datestamp DESC LIMIT 1) as loan_closed_transaction_id_date_before_the_chargeback_aka_status_16,

    /* Get date of next status 9, after the first 16: */

    (select ls.`datestamp` from loan_status ls where loan_id = l.id and status_id = 9 and datestamp > loan_closed_transaction_id_date_before_the_chargeback_aka_status_16 ORDER BY datestamp ASC LIMIT 1) as date_of_next_status_9_after_the_first_16,

    (select ls2.`datestamp` from loan_status ls2 INNER JOIN client clj ON (clj.`client_id` = ls2.`loan_id`) where clj.client_id = '3378228' and loan_id != l.id and ls2.status_id = 9 and datestamp > loan_closed_transaction_id_date_before_the_chargeback_aka_status_16 and datestamp < date_of_next_status_9_after_the_first_16 LIMIT 1) as other_loan_datestamp
) a

如何有条件地使用MYSQL别名在查询中生成列？

2 个答案: