Does the case statement in sql server have to be used with select?

does the, CASE WHEN THEN statement have to be used with the select statement in SQL server?

declare @i int
set @i=100
case @i
    when 100 then print 100
    when 200 then print 200
    else print 300
end

the above statement reported an error

Jan.13,2022
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b39359-40701.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b39359-40701.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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