左外连接:select * from T_Person left join T_Card on T_Person.CardId = T_Card.CardId
左外连接只匹配后只增加指定列:SELECT a1.*,a2.imcode FROM a1 LEFT JOIN a2 ON a1.a=a2.a
左外连接:select * from T_Person left join T_Card on T_Person.CardId = T_Card.CardId
左外连接只匹配后只增加指定列:SELECT a1.*,a2.imcode FROM a1 LEFT JOIN a2 ON a1.a=a2.a
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