以下的文章主要介绍的是MySQL 常用命令以及对MySQL 常用命令的整理，我们大家都知道MySQL 常用命令在实际应用中应用的比例是比较多的，今天我们就像大家详细介绍一下MySQL 常用命令与其整理。 是否存在 MySQL useimss; MySQL selectif(exists(select*frominf
以下的文章主要介绍的是MySQL 常用命令以及对MySQL 常用命令的整理 ，我们大家都知道MySQL 常用命令在实际应用中应用的比例是比较多的，今天我们就像大家详细介绍一下MySQL 常用命令与其整理。
是否存在
<ol class="dp-xml"> <li class="alt">MySQL<span><span class="tag">></span><span> use imss; </span></span> </li> <li>MySQL<span class="tag">></span><span> select if(exists(select * from information_schema.columns where </span><span class="attribute">table_name</span><span> = <br></span><span class="attribute-value">'imss_righttemplate'</span><span> and </span><span class="attribute">column_name</span><span>=</span><span class="attribute-value">'id_righttemplate'</span><span>),'yes','no') as cz ; </span> </li> </ol>
MySQL 常用命令整理 ：主键
<ol class="dp-xml"><li class="alt">MySQL<span><span class="tag">></span><span> alter table tabelname add new_field_id int(5) unsigned default 0 not null auto_increment ,add primary key (new_field_id); </span></span> </li></ol>
增加一个新列
<ol class="dp-xml"> <li class="alt">MySQL<span><span class="tag">></span><span> alter table t2 add d timestamp; </span></span> </li> <li>MySQL<span class="tag">></span><span> alter table infos add ex tinyint not null default '0'; </span> </li> </ol>
删除列
<ol class="dp-xml"><li class="alt">MySQL<span><span class="tag">></span><span> alter table t2 drop column c; </span></span> </li></ol>
重命名列
<ol class="dp-xml"><li class="alt">MySQL<span><span class="tag">></span><span> alter table t1 change a b integer; </span></span> </li></ol>
改变列的类型
<ol class="dp-xml"> <li class="alt">MySQL<span><span class="tag">></span><span> alter table t1 change b b bigint not null; </span></span> </li> <li>MySQL<span class="tag">></span><span>alter table infos change list list tinyint not null default '0'; </span> </li> </ol>
MySQL 常用命令整理 ：重命名表
<ol class="dp-xml"><li class="alt">MySQL<span><span class="tag">></span><span> alter table t1 rename t2; </span></span> </li></ol>
加索引
<ol class="dp-xml"> <li class="alt">MySQL<span><span class="tag">></span><span> alter table tablename change depno depno int(5) not null; </span></span> </li> <li>MySQL<span class="tag">></span><span> alter table tablename add index 索引名 (字段名1[，字段名2 …]); </span> </li> <li class="alt">MySQL<span class="tag">></span><span> alter table tablename add index emp_name (name); </span> </li> </ol>
加主关键字的索引
<ol class="dp-xml"><li class="alt">MySQL<span><span class="tag">></span><span> alter table tablename add primary key(id); </span></span> </li></ol>
加唯一限制条件的索引
<ol class="dp-xml"><li class="alt">MySQL<span><span class="tag">></span><span> alter table tablename add unique emp_name2(cardnumber); </span></span> </li></ol>
删除某个索引
<ol class="dp-xml"><li class="alt">MySQL<span><span class="tag">></span><span>alter table tablename drop index emp_name; </span></span> </li></ol>
增加字段
<ol class="dp-xml"><li class="alt">MySQL<span><span class="tag">></span><span> ALTER TABLE table_name ADD field_name field_type; </span></span> </li></ol>
修改原字段名称及类型
<ol class="dp-xml"><li class="alt">MySQL<span><span class="tag">></span><span> ALTER TABLE table_name CHANGE old_field_name new_field_name field_type; </span></span> </li></ol>
删除字段
<ol class="dp-xml"><li class="alt">MySQL<span><span class="tag">></span><span> ALTER TABLE table_name DROP field_name; </span></span> </li></ol>
以上的相关内容就是对MySQL 常用命令整理的介绍，望你能有所收获。
