Question

如果记录计数= 0，我需要以下查询来返回消息，例如“无结果”。

set @ID_CARTERA = 1;

select    

LEFT(A.F_ANOTRIMESTRE, 4 ) Year,
RIGHT(A.F_ANOTRIMESTRE, 2 ) Quarter,
ROUND ( A.POR_RENTABILIDAD, 2 ) Quarterly_Yield

from      dr_rent_carteras_trimestres A

where     A.ID_CARTERA = @ID_CARTERA
And       (LEFT(A.F_ANOTRIMESTRE, 4 ) = ( select    MAX(left(F_ANOTRIMESTRE, 4 ) ) - 0
                                         from      dr_rent_carteras_trimestres
                                         where     ID_CARTERA = @ID_CARTERA ) 
            and
            RIGHT(A.F_ANOTRIMESTRE, 2 ) = 12)

Answer 1

你可以像这样欺骗系统：

生成一个返回COUNT（*）的查询。这将始终返回一行，即使有零行计数
使用COUNT（*）查询左连接主查询。使用Case语句将结果替换为“No Results”。

因此，结果查询看起来像（假设 - 主查询只返回零或一条记录 - 因此LEFT JOIN中没有ON子句!!!!）：

set @ID_CARTERA = 1;

select    
CASE cnt WHEN 0 THEN "No Results" ELSE Year END,
Quarter,
Quarterly_Yield
FROM
(select count(*) AS cnt
from      dr_rent_carteras_trimestres A
where     A.ID_CARTERA = @ID_CARTERA
And       (LEFT(A.F_ANOTRIMESTRE, 4 ) = ( select    MAX(left(F_ANOTRIMESTRE, 4 ) ) - 0
                                         from      dr_rent_carteras_trimestres
                                         where     ID_CARTERA = @ID_CARTERA ) 
            and
            RIGHT(A.F_ANOTRIMESTRE, 2 ) = 12) ) cnt_tbl
LEFT JOIN
( select    
LEFT(A.F_ANOTRIMESTRE, 4 ) Year,
RIGHT(A.F_ANOTRIMESTRE, 2 ) Quarter,
ROUND ( A.POR_RENTABILIDAD, 2 ) Quarterly_Yield
from      dr_rent_carteras_trimestres A
where     A.ID_CARTERA = @ID_CARTERA
And       (LEFT(A.F_ANOTRIMESTRE, 4 ) = ( select    MAX(left(F_ANOTRIMESTRE, 4 ) ) - 0
                                         from      dr_rent_carteras_trimestres
                                         where     ID_CARTERA = @ID_CARTERA ) 
            and
            RIGHT(A.F_ANOTRIMESTRE, 2 ) = 12) ) main_tbl

使用UNION可以完成同样的事情。如果您希望我展示如何

MySQL IF结果计数0返回消息

1 个答案: