MySQL将表a中查询的数据插入到表b中_MySQL

MySQL将表a中查询的数据插入到表b中

<code class="sql">如果表b存在

<code class="sql"><code class="sql"><code class="sql">insert into b select * from a;</code></code></code>

<code class="sql"><code class="sql"><code class="sql">如果表b不存在

<code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql">create table b as select * from a;</code></code></code></code></code></code>

<code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql">扩展：

<code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql">将b表中的某写字段值插入到a表中

<code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql">insert into a (userID,userName) select b.userID,b.userName from tr_ajax_chat_messages;</code></code></code></code></code></code></code></code></code></code></code>

<code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql">将a表和b表userID相等的值保存到a表

<code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql"><code class="sql">update a set a.userName=(select b.userName from b where a.userID = b.userID);</code></code></code></code></code></code></code></code></code></code></code></code></code></code></code></code></code></code>