请教怎样批量更新表值
请问怎样批量更新表值
现在我有一个数据表，其中有一个字段是type。数据表中有N条信息，
我希望更改 type的值，条件是根据不同的classid来更改。
但是现在又多组条件对应的多组type值
比如当class=1时，type=rass
class=8时，type=bbcc
还有多组这样的情况，请问怎样一次性一一对应的更新完所有的type。
我自己没办法了，刚学，我能想到的就是update table set type=相应值 where class=相应值
------解决方案--------------------
CASE value WHEN [compare_value] THEN result [WHEN [compare_value] THEN result ...] [ELSE result] END
CASE WHEN [condition] THEN result [WHEN [condition] THEN result ...] [ELSE result] END
http://dev.mysql.com/doc/refman/5.1/en/control-flow-functions.html#operator_case
------解决方案--------------------
你的数据库不符合第三范式，建议分解：新建(class,type)，将type从原表中去除。
------解决方案--------------------
SQL中where查询符合条件的，然后更新
------解决方案--------------------
如果你的class和type对应关系没有规律的话，就不要用if,else或case when then来写了，不然得写多长？
你单独建立一个表，把class和type的对应关系存进去，更新表的时候与这个表做下联查
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