2关于更好地优化数据库设计的问题

Question

1) In mysql engines, MyISAM Is Better Or InnoDB ?

2) i want programming a cms that it could add a post with multi category how i must design my database to have a better performance with a few query ?

in php how can list posts which category for example = 1 ?

thank you

Answer 1

1) If you need foreign keys relations on DB level use InnoDB else use MyISAM

2) You can store all categories in one table with schema like that

create table categories (
Category_ID int NOT NULL,
ParentCategory_ID int NOT NULL default 0,
CategoryName varchar(150)
);

with Category_ID primary key

3)

$sql = select * from posts where category_id = 1;
mysql_query($sql);

edit : Schema of post table (example)

create table posts (
    Post_ID int NOT NULL,
    Category_IDs varchar(50) NOT NULL,
    POSTDescription varchar(1000),
    POSTTime int NOT NULL
)

Post_ID is primary key of posts table.

note the Category_IDs is now varchar store value of categories in it like 1,2,3 if your post belongs to cateory 1,2 and 3.. and for deleting all posts belonging to category 1 you will run following query

$sql = DELETE
FROM `posts`
WHERE FIND_IN_SET( '1', `Category_IDs` ) >0;

Answer 2

There is no definitive answer as it depends on your requirements but, lots of people will have already mentioned things such as:

• innodb has row level locking vs. myisam table locking so innodb can handle more concurrent requests.
• innodb is transactional so inserts will generally be slower than myisam
• innodb is a proper RDBMS engine so supports referential integrity (transactions ACID bla bla bla)
• innodb is more reliable than myisam
• myisam is faster than innodb for reads (myth)
• myisam tables have smaller footprints than innodb ones (myth)

However not many people will mention innodb clustered primary key indexes and how a well designed innodb table will easily out perform an equivalent myisam one because of this.

Here are two links explaining clustered indexes:

http://dev.mysql.com/doc/refman/5.0/en/innodb-index-types.html

http://www.xaprb.com/blog/2006/07/04/how-to-exploit-mysql-index-optimizations/

Also, have a look at the following examples and articles (second example may have particular relevance)

• 500 million row forum/thread example

  MySQL and NoSQL: Help me to choose the right one

• 125 million row product/category example

  Rewriting mysql select to reduce time and writing tmp to disk

• 100 million row experiment

  Optimal MySQL settings for queries that deliver large amounts of data?

• Innodb vs. myisam vs. falcon benchmarks

  http://www.mysqlperformanceblog.com/2007/01/08/innodb-vs-myisam-vs-falcon-benchmarks-part-1/

Hope this helps :)