左连接的区别

SELECT (’(’ || D.DWBH || ‘)’ || D.MC) as bm,D.DWBH，D.MC
FROM RS_JGSZ_ZZLD T
left join ac_sys_dwb D on T.ZZDWBH = d.DWBH
AND T.rybh = ‘JZG20182’
AND T.SAAS = ‘000001’ and D.DWBH is not null and D.MC is not null

SELECT (’(’ || D.DWBH || ‘)’ || D.MC) AS BM FROM AC_SYS_DWB D
LEFT JOIN RS_JGSZ_ZZLD T ON T.ZZDWBH = D.DWBH
WHERE T.RYBH = ‘JZG20182’
AND T.SAAS = ‘000001’ and D.DWBH is not null and D.MC is not null