Declare @mainString nvarchar(100)='Amit Kumar Yadav'
---Check here @mainString contains Amit or not, if it contains then retrun greater than 0 then print Find otherwise Not Find
if CHARINDEX('Amit',@mainString) > 0
begin
select 'Find' As Result
end
else
select 'Not Find' As Result
-- To find an exact string
SELECT * FROM [table] WHERE [field] LIKE '%stringtosearchfor%'.