MySQL error code 1292 -

when running query below keep getting warning:

warning | 1292 | truncated incorrect double value: 'resolved date'.

i'm trying extract strings dates str_customvalue. why did date(date(str_customvalue)) not null.

    select     case str_category         when             ('resolved date'                 , (status = 'closed')                 , (date(str_customvalue) not null)             )                     cast(str_customvalue datetime)         else cast(str_diff_date` datetime)     end last_diff_date      table 

is there way remove warning? query works fine, in order script pass qa need remove warning.

i solved issue using if() statement such:

select if ( str_category = 'resolved date' ,    , (status = 'closed')    , (date(str_customvalue) not null,     cast(str_customvalue datetime),    cast(str_diff_date` datetime))    last_diff_date  table