1、left join和 多表查询
select t1.cardtype,t1.description,t1.enabled,t1.service,t2.CARD_TYPE_GROUP_NAME from prepaid_remit_pccw_cardtype t1 left join PREPAID_REMIT_CARDTYPE_GROUP t2 on t1.card_type_group_id = t2.card_type_group_id order by t1.service,t1.cardtype
区别:
left join 所有的工作以left为准 以左表为准,所以
1 如果左表中有空,那么就会显示一条空记录
2 如果左表中有一条记录在右表中找不到,同样这条记录也会显示出来
多表查询则不然,只要where中不匹配则不显示该条记录
select t1.cardtype,t1.description,t1.enabled,t1.service,t2.CARD_TYPE_GROUP_NAME from prepaid_remit_pccw_cardtype t1 ,PREPAID_REMIT_CARDTYPE_GROUP t2 where t1.card_type_group_id = t2.card_type_group_id order by t1.service,t1.cardtype
2.多表插入
使用符合语句:
insert into prepaid_remit_pccw_cardtype t (t.cardtype,t.enabled,t.description,t.service,t.card_type_group_id) values (1,'Y','a','b',(select g.card_type_group_id from PREPAID_REMIT_CARDTYPE_GROUP g where g.card_type_group_name='ab'))