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SELECTa.*,p.pub_id,p.pub_name,p.country
FROM authors AS a INNER JOIN publishers AS p
ON a.city=p.city
(二) 外连接
外连接,返回到查询结果集合中的不仅包含符合连接条件的行,而且还包括左表(左外连接或左连接))、右表(右外连接或右连接)或两个边接表(全外连接)中的所有数据行。 left join(左联接) 返回包括左表中的所有记录和右表中联结字段相等的记录; right join(右联接) 返回包括右表中的所有记录和左表中联结字段相等的记录;
例如1:
SELECT a.*,b.* FROM luntanLEFT JOIN usertable as b
ON a.username=b.username
例如2:
SELECT a.*,b.*
FROM city as a FULL OUTER JOIN user asb
ON a.username=b.username
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