DATABASE

wordpress 的 schema

by

ver 2.7:

wp_2.7

幾個查詢例:

SELECT m.* FROM  wp_posts  p , wp_postmeta m
where p.id=m.post_id
order by post_id desc


SELECT tr.* 
FROM  wp_posts  p , wp_term_relationships tr  
where p.id=tr.object_id
order by p.id desc


SELECT p.id , w.*
FROM  wp_posts  p , wp_term_relationships tr , wp_term_taxonomy t
where p.id=tr.object_id
and tr.term_taxonomy_id=t.term_taxonomy_id
order by p.id desc


SELECT p.id , w.*
FROM  wp_posts  p , wp_term_relationships tr , wp_term_taxonomy t ,  wp_terms w
where p.id=tr.object_id
and tr.term_taxonomy_id=t.term_taxonomy_id
and t.term_id = w.term_id
order by p.id desc

MySQL – Optimizing Database Structure

by

參考: http://dev.mysql.com/doc/refman/5.0/en/optimizing-database-structure.html

7.4.1. Make Your Data as Small as Possible
7.4.2. Column Indexes
7.4.3. Multiple-Column Indexes
7.4.4. How MySQL Uses Indexes
7.4.5. The MyISAM Key Cache
7.4.6. MyISAM Index Statistics Collection
7.4.7. How MySQL Opens and Closes Tables
7.4.8. Disadvantages of Creating Many Tables in the Same Database

減少 record structure 的大小 – Numeric Types 參考表
(用 MEDIUMINT 3bytes 比 INT 4bytes 好 , 若資料內容不可能有負值那加上 UNSIGNED , 則數值範圍可多一倍!)

fd5aa2a415b47b898c229846a7644cf8

mysql index 的建立/使用 , Multiple-Column Indexes

by

http://dev.mysql.com/doc/refman/5.0/en/multiple-column-indexes.html

CREATE TABLE test (
    id         INT NOT NULL,
    last_name  CHAR(30) NOT NULL,
    first_name CHAR(30) NOT NULL,
    PRIMARY KEY (id),
    INDEX name (last_name,first_name)
);

The name index is an index over the last_name and first_name columns. The index can be used for queries that specify values in a known range for last_name, or for both last_name and first_name. Therefore, the name index is used in the following queries: 

SELECT * FROM test WHERE last_name='Widenius';

SELECT * FROM test
  WHERE last_name='Widenius' AND first_name='Michael';

SELECT * FROM test
  WHERE last_name='Widenius'
  AND (first_name='Michael' OR first_name='Monty');

SELECT * FROM test
  WHERE last_name='Widenius'
  AND first_name >='M' AND first_name < 'N';

However, the name index is not used in the following queries, 以下的 query 用不到 index —> 多重 index 有先後區別. 

SELECT * FROM test WHERE first_name='Michael';

SELECT * FROM test
  WHERE last_name='Widenius' OR first_name='Michael';

Manage Oracle Streams Advanced Queuing – DBMS_AQADM

by

 

官網資料 : http://download-west.oracle.com/docs/cd/B19306_01/appdev.102/b14258/d_aqadm.htm#i1015375

The DBMS_AQADM package provides procedures to manage Oracle Streams Advanced Queuing (AQ) configuration and administration information.

See Also:

This chapter contains the following topics: