SELECT
*
FROM
jsyd_zzbpclxx
WHERE
isvalid = 1
AND SBSJ >= to_date( '2021-01-01', 'yyyy-MM-dd' )
AND SBSJ <= to_date( '2021-12-31', 'yyyy-MM-dd' )
AND
decode( ssxzqdm, '320202', '320213', '320203', '320213', '320204', '320213', ssxzqdm ) = '320200'
ORDER BY
PZSJ DESC
这句decode函数的作用是什么?