对于查询情况,其实MySQL提供给我们一个功能来引导优化器更好的优化,那便是MySQL的查询优化提示(Query Optimizer Hints)。比如,想让SQL强制走索引的话,可以使用 FORCE INDEX 或者USE INDEX;它们基本相同,不同点:在于就算索引的实际用处不大,FORCE INDEX也得要使用索引。 EXPLAIN SELECT * FROM yp_user FORCE INDEX(...
DELETE TABLE1 where exists ( select 1 from table2 where and table1.khid=table2.khid and FWDWID=8); Sql代码 < id=Player1255328313684 pluginspage=http://www.macromedia.com/go/getflashplayer src=http://nodonkey.javaeye.com/javascripts/syntaxhighlighter/clipboard_new.swfwidth=14 height=15 type...
name} </if> </foreach> </trim> <trim prefix="age =CASE" suffix="END,"> <foreach collection="list" item="item" index="index"> <if test="item.age != null"> WHEN id=#{item.id} THEN #{item.age} </if> </foreach> </trim> </trim> WHERE id IN <foreach collection="list...
安全模式设置成功后如果再次执行全表update/delete,会报错 DELETEfromm_testerror : You are using safeupdatemodeandyou triedtoupdateatablewithout aWHEREthat uses aKEYcolumn. 总结 如果开启了安全模式后 update语句必须满足如下条件之一才能执行成功 1)使用where子句,并且where子句中列必须为prefix索引列 2)使用limi...
delete table delete kv delete kv [-key<key>] [-start prefixString] [-end prefixString] [-all] Deletes one or more keys. If-allis specified, delete all keys starting at the specified key. If no key is specified, delete all keys in the store. The-startand-endflags can be used for...
@TableField(value = "update_time",fill = FieldFill.INSERT_UPDATE) private LocalDateTime updateTime; 1. 2. 我们来试试,给user表增加create_time和update_time字段。 执行新增方法 User user = new User(); user.setNickName("程序员柳大侠"); ...
This statement changes the exam subject from Spanish to Italian. Notice that theOUTPUTclause is placed afterSET. There are also two prefixes in anUPDATEquery:InsertedandDeleted. These two prefixes allow us to see the record data both before and after the update. TheDeletedpr...
+ TABLE_PREFIX_SUBST + TABLE_LOCKS + " WHERE " + COL_LOCK_NAME + " = ? FOR UPDATE"; /* * ~~~ * * Constructors. * * ~~~ */ /** * This constructor is for using the <code>StdRowLockSemaphore</code> as * a bean.
This creates a new SQL query that deletes all tables which begin with the prefixes,wpstg0_wpstg1_andwpstg2_ SQL DROPTABLEDATABASENAME.wpstg1_options;DROPTABLEDATABASENAME.wpstg1_postmeta;DROPTABLEDATABASENAME.wpstg1_posts; In the future, WP Staging will be able to clean up those unused ...
ALTER TABLE table_name ADDKEY(column_name(prefix_length)) 10. InnoDB 与 MyISAM 索引存储结构的区别 MyISAM索引文件和数据文件是分离的,索引文件仅保存数据记录的地址。 而在InnoDB中,表数据文件本身就是按B+Tree组织的一个索引结构,这棵树的叶节点data域保存了完整的数据记录。这个索引的key是数据表的主键,...