sql - Combining different CASE expression syntaxes -

my understanding of case expression can use matching:

case expression     when first_option some_value     when second_option some_other_value     else default_value end 

and evaluating conditions:

case     when a_value = another_value some_result     when some_other_condition some_other_result     else default_value end 

but can combine both:

case expression     when first_option , a_value = another_value some_result     when second_option , some_other_condition some_other_result     else default value end 

for example, work?:

case btt_display     when 'col' , bd_trans_date = bd_posted_date 'y'     when 'dis' , bd_trans_date = bs_posted_date 'y'     else 'n' end sda_ind 

you can't combine them. 1 expects value after when, other condition.

case column when value case when condition 

attempting combine them places condition value expected.