return Y or N based on result of EXISTS subquery

What would be a good way to make this logic work in a SQL query?

select col1, col2, col3, YorN
from tab1

I want to return YorN as either a literal 'Y' or 'N' based on whether or not something EXISTS or not.

if EXISTS (select 1 from tab2 where tab1.col1 = tab2.col1) then Y
if NOT EXISTS (same as above) then select N

What's the most efficient way of doing this?
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Lee SavidgeCommented:
Something like this?

if EXISTS (select top 1 * from tab2 where tab1.col1 = tab2.col1)
    select 'Y'
    select 'N'

Open in new window

I'd suggest a CASE WHEN THEN statement along with an LEFT JOIN on tab2.  For example
SELECT    col1, col2, col3, CASE WHEN B.Col1 IS NULL THEN 'N' ELSE 'Y' END AS [YorN]
FROM        tab1 AS A
                 LEFT JOIN tab2 AS B ON A.col1=B.col1

Assuming col1 is indexed appropriately, this should get you the best performance

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Microsoft SQL Server 2005

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