标题: SQL中INNER JOIN的问题 [打印本页] 作者: shiyiming 时间: 2004-5-13 04:40 标题: SQL中INNER JOIN的问题 下面是从SAS网站上看到的程序，希望知道这两个程序是否有区别，结果似乎一样，是否有其他方面的区别。
proc sql;
title 'Inner Join';
select *
from lefttab as l, righttab as r
where l.continent=r.continent;
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proc sql;
title 'Inner Join';
select *
from lefttab as l inner join
righttab as r
on l.continent=r.continent;作者: shiyiming 时间: 2004-5-13 07:59
I think there is no difference if the syntax for the second one is correct. The first one is the syntax mostly used for inner join, I have never tried to write something as the second one. Surely, the left join, right join and full join follows the syntax as the second one.作者: shiyiming 时间: 2004-5-13 10:32 标题: re: 我个人觉得这两个程序并没有太大的区别:
它们执行后的结果是相同的.要说区别那可能就是它们在执行过程不同:
proc sql;
title 'Inner Join';
select *
from lefttab as l, righttab as r
where l.continent=r.continent;
//这段程序是从两张表中取记录,然后比较字段continent,得到结果.
proc sql;
title 'Inner Join';
select *
from lefttab as l inner join
righttab as r
on l.continent=r.continent;
//这段程序就是先将两张表进行连接,然后在连接后的结果中进行删选.得到结果.
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个人想法!