Power bi DAX findout 2nd MAX value

[BIswajit_Das]

Hello Guys,
I have a table like

item	res	a
1	a	30.98
1	b	30.98
1	c	20.34
1	d	17.7

and
my required table is like

item	res	a	max	2nd	gap
1	a	30.98	30.98	30.98	0
1	b	30.98	30.98	30.98	0
1	c	20.34	30.98	30.98	0
1	d	17.7	30.98	30.98	0

when i calculated its hard to detect max cause both a and b have same values so the coming 2nd max result is wrong
i.e the coming result is like

item	res	a	max	2nd	gap
1	a	30.98	30.98	20.34	10.64
1	b	30.98	30.98	20.34	10.64
1	c	20.34	30.98	20.34	10.64
1	d	17.7	30.98	20.34	10.64

Thanks & Regrads...

[BIswajit_Das]

Hello @Ahmedx thanks for responding but

my required result table should like

item	res	a	max	2nd	gap
1	a	30.98	30.98	30.98	0
1	b	30.98	30.98	30.98	0
1	c	20.34	30.98	30.98	0
1	d	17.7	30.98	30.98	0

[Greg_Deckler]

@BIswajit_Das Try:

max a 2nd = 
    VAR __Item = MAX('Table'[item])
    VAR __Table = FILTER(ALL('Table'), [item] = __Item)
    VAR __Summarized = SUMMARIZE(__Table, [item], [a], "__Count", COUNTROWS('Table'))
    VAR __Max = MAXX(__Table, [a])
    VAR __Result = 
        IF(
            MAXX(FILTER(__Summarized, [a] = __Max),[__Count]) > 1,
            __Max,
            MAXX(FILTER(__Summarized, [a] < __Max), [a])
        )
RETURN
    __Result

[BIswajit_Das]

Hello @Greg_Deckler  Thanks for responding but what if i have multiple Items
i.e

item	res	a	max	2nd	gap
1	a	30.98	30.98	30.98	0
1	b	30.98	30.98	30.98	0
1	c	20.34	30.98	30.98	0
1	d	17.7	30.98	30.98	0
2	a	55	55	45	10
2	b	45	55	45	10
3	a	35	65	35	30
3	c	65	65	35	30

[Ahmedx]

Based on your description, I created data to reproduce your scenario. The pbix file is attached in the end.

Power bi DAX findout 2nd MAX value.pbix