SELECT
    table.col1 as 'col1',
    (case 
        when table.col2 = 0 then 'col2为0' 
        when table.col2 = 1 then 'col2为1' 
        when table.col2 = 2 then 'col2为2' 
        else 'col2为0、1、2之外的值' end ) as 'col2',
    table.col3 as 'col3'
FROM
    table
WHERE table.col3 = '1'