blocks|key|1897911|text|正如您所写的，OUTER确实是多余的，因为所有的OUTER连接要么是LEFT，要么是RIGHT，反过来，所有的LEFT或RIGHT连接都是OUTER。正如你所说，从句法上讲，它主要是噪音。即使在ISO+SQL中，它也是可选的。至于为什么人们使用它，我想有些人觉得有必要坚持连接是OUTER的，即使left-or-right关键字已经说明了这一点。就这一点而言，INNER也是多余的！|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1897912|entityMap^0|7|5|O|5|Y|4|16|5|1J|4|1O|5|1X|5|3V|5|50|5|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]|$9|Q|A|R|B|C]|$9|S|A|T|B|C]|$9|U|A|V|B|C]|$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|G|$]]

<code>OUTER</code> really is superfluous, as you write, since all <code>OUTER</code> joins are either <code>LEFT</code> or <code>RIGHT</code>, and reciprocally all <code>LEFT</code> or <code>RIGHT</code> joins are <code>OUTER</code>. So syntactically it's mostly noise, as you put it. It is optional even in ISO SQL. As for why people use it, I suppose some feel the need the insist on the join being <code>OUTER</code>, even if the left-or-right keyword already says so. For that matter, <code>INNER</code> also is superfluous!

blocks|key|511915|text|是的|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|511916|在我看来，这只会让事情变得更清晰--你陈述的意图越清晰越明显(特别是对于后来试图阅读和理解你的代码的其他人来说)。|511917|但这只是我的观点-在技术上不需要，所以你可以使用它-或者离开它。|511918|entityMap^0|0|2|0|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|O|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|P|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|K|$]]

YES 

It just make things clearer in my opinion - the clearer and more obvious you state your intent, the better (especially for someone else trying to read and understand your code later on).

But that's just my opinion - it's not technically needed, so you can use it - or leave it.

blocks|key|511967|text|不是的。我使用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|511968|511969|JOIN+|unordered-list-item|511970|LEFT+JOIN|511971|RIGHT+JOIN+|511972|FULL+OUTER+|511973|CROSS+JOIN|511974|511975|这对我来说是没有歧义的。|511976|entityMap^0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|T|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|U|8|@]|9|@]|A|$]]|$1|F|3|G|5|E|7|V|8|@]|9|@]|A|$]]|$1|H|3|I|5|E|7|W|8|@]|9|@]|A|$]]|$1|J|3|K|5|E|7|X|8|@]|9|@]|A|$]]|$1|L|3|M|5|E|7|Y|8|@]|9|@]|A|$]]|$1|N|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|10|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|R|$]]

No. I use

<ul>
<li>JOIN </li>
<li>LEFT JOIN</li>
<li>RIGHT JOIN </li>
<li>FULL OUTER JOIN </li>
<li>CROSS JOIN</li>
</ul>

There is no ambiguity for me.

blocks|key|511799|text|Stackoverflow上的几个月告诉我的一件事是，没有接触过SQL或关系数据库的人编写和/或维护了多少SQL。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|511800|出于这个原因，我认为当你看你的代码时，你越明确，下一个程序员就会越好。|511801|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

One thing that several months on Stackoverflow has shown me is how much SQL is written and / or maintained by people with no previous exposure to SQL or relational databases at all.

For that reason, I think that the more explicit you can be the better off the next programmer is going to be when looking at your code.

blocks|key|1897870|text|这只是一个品味问题，我猜人们使用它是因为他们发现它会带来更多的可读性代码。例如，我更喜欢使用also+optional+AS关键字，因为对于我来说，SELECT+...+FROM+table+AS+t看起来比SELECT+...+FROM+table+t更具可读性。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1897871|entityMap^0|22|Q|2W|N|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

It is simply a matter of taste, I guess that people use it because they find that it leads to more readable code. For example, I prefer to use the also optional AS keyword since <code>SELECT ... FROM table AS t</code> looks more readable than <code>SELECT ... FROM table t</code> for me.

blocks|key|1811314|text|我使用了“inner+join”、“left+join”、“right+join”和“full+outer+join”。‘'join’没有'inner‘使它对我来说有点模棱两可；'left’和'right‘是自我描述的，而'full’是一种需要特殊语法的野兽:)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1811315|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I'm using 'inner join', 'left join', 'right join', and 'full outer join'. 'join' without 'inner' makes it somewhat ambigious to me; 'left' and 'right' are self-descriptive and 'full' is such kind of a beast that it deserves special syntax :)

blocks|key|1811343|text|我自己使用OUTER关键字。我同意这只是一个品味问题，但省略它让我觉得有点草率，但没有省略SQL关键字(+sloppy+)或用小写写INNER关键字(非常草率)那么糟糕。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1811344|entityMap^0|5|5|1U|5|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

I use the <code>OUTER</code> keyword myself. I agree it is merely a matter of taste but omitting it strikes me as being a little sloppy but not as bad a omitting the <code>INNER</code> keyword (sloppy) or writing SQL keywords in lower case (very sloppy).

blocks|key|1898115|text|我认为在2009年没有可移植的SQL这回事…在某些情况下，您需要编写特定于DBMS的语句(比如检索前N行)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1898116|我个人认为连接语法是多余的，我用逗号分隔表名。|1898117|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

I think there is no such thing as portable SQL in the year 2009 anyway... At some point, you need to write DBMS-specific statements (like retrieving top N rows).

I personally find the JOIN syntax redundant and instead I comma-separate table names.

I often see people who write SQL like this:

<pre><code>SELECT * from TableA LEFT OUTER JOIN TableB ON (ID1=I2)
</code></pre>

I myself write simply:

<pre><code>SELECT * from TableA LEFT JOIN TableB ON (ID1=I2)
</code></pre>

To me the "OUTER" keyword is like line noise - it adds no additional information, just clutters the SQL. It's even optional in most RDBMS that I know. So... why do people still write it? Is it a habit? Portability? (Are your SQL's really portable anyway?) Something else that I'm not aware of?

Do you use the OUTER keyword when writing left/right JOINs in SQL?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我经常看到这样编写SQL的人：SELECT * from TableA LEFT OUTER JOIN TableB ON (ID1=I2)我自己写的很简单：SELECT * from TableA LEFT JOIN TableB ON (ID1=I2)对我来说，“just”关键字就像是行噪声--它不会添加任何额外的信息，只会使SQL变得混乱。据我所知，它甚至在大多数RDBMS中都是可选的。所以

问在SQL中编写left/right连接时是否使用OUTER关键字？
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问在SQL中编写left/right连接时是否使用OUTER关键字？
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