blocks|key|1045540|text|更新条目：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1045541|一个简单的增量应该可以解决这个问题。|1045542|UPDATE+mytable+
++SET+logins+=+logins+%2B+1+
++WHERE+id+=+12|code-block|syntax|javascript|1045543|插入新行，或更新(如果已存在)：|1045544|如果您想要更新以前存在的行，或者在它不存在时插入它，您可以使用REPLACE+syntax或INSERT...ON+DUPLICATE+KEY+UPDATE选项(就像Rob+Van+Dam在his+answer中演示的那样)。|offset|length|style|CODE|1045545|插入新条目：|1045546|或者你正在寻找像INSERT...MAX(logins)%2B1这样的东西？从本质上讲，您将运行如下所示的查询-根据您的特定需求，可能会更复杂一些：|1045547|INSERT+into+mytable+(logins)+
++SELECT+max(logins)+%2B+1+
++FROM+mytable|1045548|entityMap|0|LINK|mutability|MUTABLE|url|http://dev.mysql.com/doc/refman/5.0/en/replace.html|1|http://dev.mysql.com/doc/refman/5.0/en/insert-on-duplicate.html|2|https://stackoverflow.com/users/232706/rob-van-dam|3|https://stackoverflow.com/questions/2762851/increment-a-database-field-by-1/2762975#2762975|4|https://stackoverflow.com/questions/1587562/problem-with-mysql-insert-max1^0|0|0|0|0|V|7|1A|W|V|E|0|1A|W|1|2B|B|2|2N|A|3|0|0|8|M|8|M|4|0|0^^$0|@$1|2|3|4|5|6|7|1C|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1D|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|1E|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|1F|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|1G|8|@$M|1H|N|1I|O|P]|$M|1J|N|1K|O|P]]|9|@$M|1L|N|1M|1|1N]|$M|1O|N|1P|1|1Q]|$M|1R|N|1S|1|1T]|$M|1U|N|1V|1|1W]]|A|$]]|$1|Q|3|R|5|6|7|1X|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|1Y|8|@$M|1Z|N|20|O|P]]|9|@$M|21|N|22|1|23]]|A|$]]|$1|U|3|V|5|F|7|24|8|@]|9|@]|A|$G|H]]|$1|W|3|-4|5|6|7|25|8|@]|9|@]|A|$]]]|X|$Y|$5|Z|10|11|A|$12|13]]|14|$5|Z|10|11|A|$12|15]]|16|$5|Z|10|11|A|$12|17]]|18|$5|Z|10|11|A|$12|19]]|1A|$5|Z|10|11|A|$12|1B]]]]

<h3>Updating an entry:</h3>

<p>A simple increment should do the trick.</p>

<pre><code>UPDATE mytable 
  SET logins = logins + 1 
  WHERE id = 12
</code></pre>

<h3>Insert new row, or Update if already present:</h3>

<p>If you would like to update a previously existing row, or insert it if it doesn't already exist, you can use the <a href="http://dev.mysql.com/doc/refman/5.0/en/replace.html" rel="noreferrer"><code>REPLACE</code> syntax</a> or the <a href="http://dev.mysql.com/doc/refman/5.0/en/insert-on-duplicate.html" rel="noreferrer"><code>INSERT...ON DUPLICATE KEY UPDATE</code></a> option (As <a href="https://stackoverflow.com/users/232706/rob-van-dam">Rob Van Dam</a> demonstrated in <a href="https://stackoverflow.com/questions/2762851/increment-a-database-field-by-1/2762975#2762975">his answer</a>).</p>

<h3>Inserting a new entry:</h3>

<p>Or perhaps you're looking for something like <a href="https://stackoverflow.com/questions/1587562/problem-with-mysql-insert-max1"><code>INSERT...MAX(logins)+1</code></a>? Essentially you'd run a query much like the following - perhaps a bit more complex depending on your specific needs:</p>

<pre><code>INSERT into mytable (logins) 
  SELECT max(logins) + 1 
  FROM mytable
</code></pre>


blocks|key|1260494|text|你没有说你想要做什么，但你在另一个答案的评论中暗示得足够好了。我想您可能正在寻找一个自动增量列|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1260495|create+table+logins+(userid+int+auto_increment+primary+key,+
++username+varchar(30),+password+varchar(30));|code-block|syntax|javascript|1260496|那么在插入时就不需要特殊的代码了。只是|1260497|insert+into+logins+(username,+password)+values+('user','pass');|1260498|当您在客户机代码中执行此语句时，MySQL+API有一些函数可以告诉您创建了什么用户in。|1260499|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

<p>You didn't say what you're trying to do, but you hinted at it well enough in the comments to the other answer. I think you're probably looking for an auto increment column</p>

<pre><code>create table logins (userid int auto_increment primary key, 
  username varchar(30), password varchar(30));
</code></pre>

<p>then no special code is needed on insert. Just</p>

<pre><code>insert into logins (username, password) values ('user','pass');
</code></pre>

<p>The MySQL API has functions to tell you what userid was created when you execute this statement in client code.</p>


blocks|key|1260537|text|如果您可以安全地将(firstName，lastName)作为主键，或者至少将唯一键放在主键上，那么您可以这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1260538|INSERT+INTO+logins+(firstName,+lastName,+logins)+VALUES+('Steve',+'Smith',+1)
ON+DUPLICATE+KEY+UPDATE+logins+=+logins+%2B+1;|code-block|syntax|javascript|1260539|如果您不能做到这一点，那么您必须首先获取主键，所以我认为您不能在一个查询中实现您想要的。|1260540|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

<p>If you can safely make (firstName, lastName) the PRIMARY KEY or at least put a UNIQUE key on them, then you could do this:</p>

<pre><code>INSERT INTO logins (firstName, lastName, logins) VALUES ('Steve', 'Smith', 1)
ON DUPLICATE KEY UPDATE logins = logins + 1;
</code></pre>

<p>If you can't do that, then you'd have to fetch whatever that primary key is first, so I don't think you could achieve what you want in one query.</p>


blocks|key|1045649|text|我不是MySQL方面的专家，但你可能应该看看触发器，例如在插入之前。在触发器中，您可以在原始表上运行select查询，如果它发现了什么，只需更新行'logins‘，而不是插入新值。但所有这些都取决于您运行的MySQL版本。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1045650|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|$]]

<p>I not expert in MySQL but you probably should look on triggers e.g. BEFORE INSERT.
In the trigger you can run select query on your original table and if it found something just update the row 'logins' instead of inserting new values. 
But all this depends on version of MySQL you running. </p>


<p>With MySQL, if I have a field, of say logins, how would I go about updating that field by 1 within a sql command?</p>

<p>I'm trying to create an INSERT query, that creates firstName, lastName and logins.  However if the combination of firstName and lastName already exists, increment the logins by 1.</p>

<p>so the table might look like this..</p>

<pre><code>firstName----|----lastName----|----logins

John               Jones             1
Steve              Smith             3
</code></pre>

<p>I'm after a command that when run, would either insert a new person (i.e. Tom Rogers) or increment logins if John Jones was the name used..</p>


Increment a database field by 1

MySQL

在MySQL中，如果我有一个字段，比如登录，我该如何在sql命令中用1来更新这个字段呢？我正在尝试创建一个INSERT查询，它创建firstName、lastName和登录。但是，如果firstName和lastName的组合已经存在，则将登录次数增加1。所以表可能是这样的..firstName----|----las...

问将数据库字段递增1
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