SELECT 

d.ID,d.CARDNUM,d.CARDTYPE,d.SERVICECODE,d.USERNUM,d.PWD,d.USERNAME,d.PHONE,d.STATUS,d.CLOSEREASON,d.WXUNIONID,d.GZHOPENID,d.XCXOPENID,d.WXNICKNAME,d.ALIPAYID,d.ALIPAYNICKNAME,d.BALANCE,d.CARDVALIDITYTIME,d.PAYPASSWORD,d.CREATETIME,d.CREATEUSER,d.UPDATETIME,d.UPDATEUSER,d.EXT1,d.EXT2,d.EXT3,d.CARDUID,d.CARDSN,d.USERPAYTYPE,d.WALLET1,d.WALLET2,d.WALLET3,d.WALLET4,d.WALLET5,d.ISADMIN,d.CERTTYPE,d.CERTNUM,d.WHITELISTVERSION,d.EXTENDACCOUNT,d.ORGCODE,d.PID,d.SEX,d.SCHOOLYEAR,d.PIDTITLE

FROM TB_ZHGX_CAMPUS_CARD d

LEFT JOIN TB_ZHGX_DEPARTMENT t ON t.ORGCODE=d.ORGCODE

WHERE  d.usernum='123456803'

一条记录：

另一张表：

select * 

from TB_ZHGX_DEPARTMENT  where ORGCODE='3440'

3.左连接记录数为：

SELECT 

d.ID,d.CARDNUM,d.CARDTYPE,d.SERVICECODE,d.USERNUM,d.PWD,d.USERNAME,d.PHONE,d.STATUS,d.CLOSEREASON,d.WXUNIONID,d.GZHOPENID,d.XCXOPENID,d.WXNICKNAME,d.ALIPAYID,d.ALIPAYNICKNAME,d.BALANCE,d.CARDVALIDITYTIME,d.PAYPASSWORD,d.CREATETIME,d.CREATEUSER,d.UPDATETIME,d.UPDATEUSER,d.EXT1,d.EXT2,d.EXT3,d.CARDUID,d.CARDSN,d.USERPAYTYPE,d.WALLET1,d.WALLET2,d.WALLET3,d.WALLET4,d.WALLET5,d.ISADMIN,d.CERTTYPE,d.CERTNUM,d.WHITELISTVERSION,d.EXTENDACCOUNT,d.ORGCODE,d.PID,d.SEX,d.SCHOOLYEAR,d.PIDTITLE

FROM TB_ZHGX_CAMPUS_CARD d

LEFT JOIN TB_ZHGX_DEPARTMENT t ON t.ORGCODE=d.ORGCODE

WHERE  d.usernum='123456803'

在整个表链接中出现拼接的结果集合如下：

使用链接语句发现：

SELECT 

*

FROM TB_ZHGX_CAMPUS_CARD d

LEFT JOIN TB_ZHGX_DEPARTMENT t ON t.ORGCODE=d.ORGCODE

WHERE  d.usernum='123456803'

当数据量比较大时，考虑分页查询这样就不会出现数据量过大的问题了，不必在Action中关联了