PostgreSQL 常è¦åé¡ï¼FAQï¼
                                       
   æè¿æ´æ°ï¼2007 å¹´ 2 æ 8 æ¥ ææäº 22:43:13 EST
   ä¸æçæè¿æ´æ°ï¼2007 å¹´ 2 æ 12 æ¥ ææä¸ 12:00:04 CST
   
   ç¶åç¶è·äººå¡ï¼Bruce Momjian (pgman@candle.pha.pa.us)
   æ£é«ä¸æçç¶è·äººå¡ï¼éæç(ChaoYi, Kuo)ï¼kuo.chaoyi@gmail.comï¼
   
   æ¬ææªçææ°çæ¬å¯ä»¥å¨
   http://www.postgresql.org/files/documentation/faqs/FAQ.html æ¥çã
   
   èä½æ¥ç³»çµ±å¹³å°ç¸éçåé¡å¯å¨ http://www.postgresql.org/docs/faq/
   裡æ¾å°çæ¡ã
     _________________________________________________________________
   
常è¦åé¡

   1.1)PostgreSQL æ¯ä»éº¼ï¼è©²æ麼ç¼é³ï¼
   1.2)誰æ§å¶å管çPostgreSQL ï¼
   1.3)PostgreSQLççæ¬æ¯ä»éº¼ï¼
   1.4)PostgreSQLå¯ä»¥éè¡å¨åªäºä½æ¥ç³»çµ±å¹³å°ä¸ï¼
   1.5)æå¾åªè£¡è½å¾å°PostgreSQLï¼
   1.6)ææ°çç PostgreSQL æ¯ä»éº¼ï¼
   1.7)æå¾åªè£¡è½å¾å°å° PostgreSQL çæ¯æï¼
   1.8)æå¦ä½æ交ä¸å BUG å ±åï¼
   1.9)æå¦ä½ç解已ç¥ç BUG ææ«ç¼ºçåè½ï¼
   1.10)è½å¤ ç²åçææ°ææªæåªäºï¼
   1.11)ææ該æ樣å¸ç¿ SQL ï¼
   1.12)å¦ä½æ交è£ä¸ææ¯å å¥éç¼éä¼ï¼
   1.13)PostgreSQL åå¶ä»è³æ庫系統æ¯èµ·ä¾å¦ä½ï¼
   1.14)PostgreSQL å¯ä»¥èçæè¿ååå家å¤æå¶çè®ååï¼
   
ç¨æ¶å®¢æ¶ç«¯åé¡

   2.1)æåå¯ä»¥ç¨ä»éº¼èªè¨å PostgreSQL é²è¡æºéï¼
   2.2)æä»éº¼å·¥å·å¯ä»¥æ PostgreSQL ç¨æ¼ Web é é¢ï¼
   2.3)PostgreSQL ææåå½¢ç¨æ¶çé¢(GUI)åï¼
   
系統管çåé¡

   3.1)ææ樣æè½æ PostgreSQL è£å¨ /usr/local/pgsql 以å¤çå°æ¹ï¼
   3.2)æå¦ä½æ§å¶ä¾èªå¶ä»é»è¦çé£æ¥ï¼
   3.3)ææ樣調æ´è³æ庫伺æå¨ä»¥ç²å¾æ´å¥½çæ§è½ï¼
   3.4)PostgreSQL 裡å¯ä»¥ç²å¾ä»éº¼æ¨£ç調試ç¹æ§ï¼
   3.5)çºä»éº¼å¨è©¦åé£æ¥ç»éææ¶å°ãSorry, too many clientsã è¨æ¯ï¼
   3.6)PostgreSQL çåç´éç¨æåªäºå§å®¹ï¼
   3.7)(ä½¿ç¨ PostgreSQL )æéè¦ä½¿ç¨ä»éº¼é»è¦ç¡¬é«ï¼
   
æä½åé¡

   4.1) å¦ä½åªé¸æä¸åæ¥è©¢çµæçé å¹¾è¡ï¼ææ¯é¨æ©çä¸è¡ï¼
   4.2) å¦ä½æ¥ç表ãç´¢å¼ãè³æ庫以åç¨æ¶çå®ç¾©ï¼å¦ä½æ¥ç psql
   裡ç¨å°çæ¥è©¢æ令並顯示å®åï¼
   4.3) å¦ä½æ´æ¹ä¸åæ¬ä½çè³æé¡åï¼
   4.4) å®çè¨éï¼å®ä¸è¡¨ï¼ä¸åè³æ庫çæ大éå¶æ¯å¤å°ï¼
   4.5) åå²ä¸åå¸åçææ¬æ件裡çè³æéè¦å¤å°ç£ç¢ç©ºéï¼
   4.6) çºä»éº¼æçæ¥è©¢å¾æ¢ï¼çºä»éº¼éäºæ¥è©¢æ²æå©ç¨ç´¢å¼ï¼
   4.7) æå¦ä½æè½çå°æ¥è©¢åªåå¨æ¯æ樣è©ä¼°èçæçæ¥è©¢çï¼
   4.8) ææ樣åæ£å表éå¼æç´¢å大å°å¯«ç¡éçæ­
   £å表éå¼æ¥æ¾ï¼æ樣å©ç¨ç´¢å¼é²è¡å¤§å°å¯«ç¡éæ¥æ¾ï¼
   4.9) å¨ä¸åæ¥è©¢è£¡ï¼ææ樣檢測ä¸åæ¬ä½æ¯å¦çº
   NULLï¼æå¦ä½æè½æºç¢ºæåºèä¸è«ææ¬ä½æ¯å¦å«NULLå¼ï¼
   4.10) å種å符é¡åä¹éæä»éº¼ä¸åï¼
   4.11.1) ææ樣åµå»ºä¸ååºåèåææ¯èªåéå¢çæ¬ä½ï¼
   4.11.2) æå¦ä½ç²å¾ä¸åæå¥çåºåèçå¼ï¼
   4.11.3) åæä½¿ç¨ currval() æå°è´åå¶ä»ç¨æ¶çè¡çªææ³åï¼
   4.11.4) çºä»éº¼ä¸å¨äºåç°å¸¸ä¸æ¢å¾éç¨åºåèå¢ï¼çºä»éº¼å¨åºåèæ¬ä½çåå¼ä¸­
   åå¨éæ·å¢ï¼
   4.12) ä»éº¼æ¯ OIDï¼ä»éº¼æ¯ CTID ï¼
   4.13) çºä»éº¼ææ¶å°é¯èª¤è³è¨ãERROR: Memory exhausted in
   AllocSetAlloc()ãï¼
   4.14) æå¦ä½æè½ç¥éæéè¡ç PostgreSQL ççæ¬ï¼
   4.15) æå¦ä½åµå»ºä¸åé è¨å¼æ¯ç¶åæéçæ¬ä½ï¼
   4.16) å¦ä½å·è¡å¤é£æ¥ï¼outer joinï¼æ¥è©¢ï¼
   4.17) å¦ä½å·è¡æ¶åå¤åè³æ庫çæ¥è©¢ï¼
   4.18) å¦ä½è®å½æ¸è¿åå¤è¡æå¤åè³æï¼
   4.19) çºä»éº¼æå¨ä½¿ç¨ PL/PgSQL å½æ¸ååè¨æ表æææ¶å°é¯èª¤è³è¨ãrelation
   with OID ##### does not existãï¼
   4.20) ç®åæåªäºè³æè¤å¯«(replication)æ¹æ¡å¯ç¨ï¼
   4.21) çºä½æ¥è©¢çµæ顯示ç表åææ¬åèæçæ¥è©¢èªå¥ä¸­
   çä¸åï¼çºä½å¤§å¯«çæä¸è½ä¿çï¼
     _________________________________________________________________
   
常è¦åé¡

  1.1) PostgreSQL æ¯ä»éº¼ï¼è©²æ麼ç¼é³ï¼
  
   PostgreSQL è®ä½ Post-Gres-Q-Lï¼ææåä¹ç°¡ç¨±çºPostgres
   ãæ³è½ä¸ä¸å¶ç¼é³ç人å¡å¯å¾é裡ä¸è¼è²é³æä»¶ï¼ MP3 æ ¼å¼ ã
   
   PostgreSQL æ¯é¢åç®æ¨çéä¿è³æ庫系統ï¼å®å·æå³çµ±å業
   è³æ庫系統çææåè½ï¼åæåå«æå°å¨ä¸ä¸ä»£ DBMS
   系統ç使ç¨çå¢å¼·ç¹æ§ãPostgreSQL
   æ¯èªç±åè²»çï¼ä¸¦ä¸æææºä»£ç¢¼é½å¯ä»¥ç²å¾ã
   
   PostgreSQL
   çéç¼éä¼ä¸»è¦çºå¿é¡èï¼ä»åéä½ä¸çåå°ä¸¦ééäºè¯ç¶²é²è¡è¯ç¹«ï¼éæ¯ä¸å社åéç¼é
    ç®ï¼å®ä¸è¢«ä»»ä½å¬å¸æ§å¶ã
   å¦æ³å å¥éç¼éä¼ï¼è«åè¦éç¼äººå¡å¸¸è¦åé¡ï¼FAQï¼
   http://www.postgresql.org/files/documentation/faqs/FAQ_DEV.html
   
  1.2) 誰æ§å¶ PostgreSQL ï¼
  
   å¦æä½ å¨å°æ¾PostgreSQLçæé人ï¼ææ¯ä»éº¼ä¸­
   央å§å¡æï¼ææ¯ä»éº¼æ屬å¬å¸ï¼ä½ åªè½æ¾æ£äº---å çºä¸åä¹ä¸å­
   å¨ï¼ä½æåç確æä¸å æ ¸å¿å§å¡æåCVS管ççµï¼ä½éäºå·¥ä½çµç設
   ç«ä¸»è¦æ¯çºäºé²è¡ç®¡çå·¥ä½èä¸æ¯å°PostgreSQLé²è¡ç¨ä½å¼æ§å¶ï¼PostgreSQLé
    ç®æ¯ç±ä»»ä½äººå
   å¯åå çéç¼äººå¡ç¤¾ååææç¨æ¶æ§å¶çï¼ä½ æéè¦åçå°±æ¯è¨é±éµä»¶å表ï¼åèè¨è«å³å
   ¯ï¼è¦åèPostgreSQLçéç¼è©³è¦ éç¼äººå¡å¸¸åé¡ (Developer's FAQ) ç²åè³è¨ï¼ã
   
  1.3) PostgreSQL ççæ¬æ¯ä»éº¼?
  
   PostgreSQLçç¼å¸éµå¾ç¶å¸ç BSD çæ¬ãå®å許ç¨æ¶ä¸éç®çå°ä½¿ç¨
   PostgreSQLï¼çè³ä½ å¯ä»¥é·å® PostgreSQL
   èä¸å«æºä»£ç¢¼ä¹å¯ä»¥ï¼å¯ä¸çéå¶å°±æ¯ä½ ä¸è½å è»é«èªèº«åé¡èåæå追訴æ³å¾
   責任ï¼å¦å¤å°±æ¯è¦æ±ææçè»é«æ·è²ä¸é åæ¬ä»¥ä¸çæ¬è²æã
   ä¸é¢å°±æ¯æåæ使ç¨çBSDçæ¬è²æå§å®¹ï¼
   
   PostgreSQL è³æ庫管ç系統
   
   é¨åçæ¬ï¼cï¼1996-2005ï¼PostgreSQL å¨çéç¼å°çµï¼é¨åçæ¬ï¼cï¼1994-1996
   å å·å¤§å¸è£äº
   
   ï¼Portions copyright (c) 1996-2005,PostgreSQL Global Development Group
   Portions Copyright (c) 1994-6 Regents of the University of
   Californiaï¼
   
   å許çºä»»ä½ç®ç使ç¨ï¼æ·è²ï¼ä¿®æ¹ååç¼éåè»é«åå®çææªèä¸æ¶åä»»ä½è²»ç¨ï¼
   並ä¸ç¡é 簽署å æ¤èç¢ççèæï¼åææ¯ä¸é¢ççæ¬è²æåæ¬æ®µä»¥åä¸é¢å©æ®µæå­
   åºç¾å¨æææ·è²ä¸ã
   
   ï¼Permission to use, copy, modify, and distribute this software and
   its documentation for any purpose, without fee, and without a written
   agreement is hereby granted, provided that the above copyright notice
   and this paragraph and the following two paragraphs appear in all
   copies.ï¼
   
   å¨ä»»ä½ææ³ä¸ï¼å å·å¤§å¸é½ä¸æ¿æå 使ç¨æ­
   ¤è»é«åå¶ææªèå°è´çå°ä»»ä½ç¶äºäººçç´æ¥çï¼
   éæ¥çï¼ç¹æ®çï¼éå çæèç¸ä¼´èççæå£ï¼åæ¬å©çæ失ç責任ï¼å³ä½¿å å·å¤§å­
   ¸å·²ç¶å»ºè°äºéäºæ失çå¯è½æ§æä¹æ¯å¦æ¤ã
   
   ï¼IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY
   PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL
   DAMAGES, INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS
   SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA
   HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.ï¼
   
   å å·å¤§å¸æ確æ¾æ£ä»»ä½ä¿èï¼åæ¬ä½ä¸å±éæ¼æä¸ç¹å®ç¨éçåæ¥åå©ççé±å«ä¿èã
   é裡æä¾çé份è»é«æ¯åºæ¼ãç¶ä½æ¯ãçåºç¤çï¼å èå å·å¤§å¸æ²æ責任æä¾ç¶­
   è·ï¼æ¯æï¼æ´æ°ï¼å¢å¼·æèä¿®æ¹çæåã
   
   ï¼THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
   INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
   MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
   PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
   CALIFORNIA HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE, SUPPORT,
   UPDATES, ENHANCEMENTS, OR MODIFICATIONS.ï¼
   
  1.4) PostgreSQL å¯ä»¥éè¡å¨åªäºä½æ¥ç³»çµ±å¹³å°ä¸ï¼
  
   ä¸è¬èªªä¾ï¼ä»»ä½ç¾å¨å° UNIX ç¸å®¹çä½æ¥ç³»çµ±ä¹ä¸é½è½éè¡ PostgreSQL
   ãå¨å®è£æå裡ååºäºç¼ä½æç¶éæ確測試çå¹³å°ã
   
   PostgreSQL ä¹å¯ä»¥ç´æ¥éè¡å¨åºæ¼å¾®è» Windows-NT çä½æ¥ç³»çµ±ï¼å¦
   Win2000 SP4ï¼WinXP å Win2003ï¼å·²è£½ä½å®æçå®è£åå¯å¾
   http://pgfoundry.org/projects/pginstallerä¸è¼ï¼åºæ¼MSDOSçWindowsä½æ¥­
   系統 ï¼Win95ï¼Win98ï¼WinMeï¼éè¦ééCygwin模æ¬ç°å¢éè¡PostgreSQLã
   
   åæä¹æä¸åçº Novell Netware 6 éç¼ççæ¬å¯å¾ http://forge.novell.com
   ç²åï¼çºOS/2(eComStation)éç¼ççæ¬å¯å¾
   http://hobbes.nmsu.edu/cgi-bin/h-search?sh=1&button=Search&key=postgre
   SQL&stype=all&sort=type&dir=%2F ä¸è¼ã
   
  1.5) æå¾åªè£¡è½å¾å° PostgreSQLï¼
  
   ééç覽å¨å¯å¾ http://www.postgresql.org/ftp/ ä¸è¼ï¼ä¹å¯ééFTPï¼å¾
   ftp://ftp.PostgreSQL.org/pub/ ç«é»ä¸è¼ã
   
  1.6) ææ°çç PostgreSQL æ¯ä»éº¼ï¼
  
   PostgreSQL ææ°ççæ¬æ¯çæ¬ 8.2.3 ã
   
   æåè¨åæ¯å¹´ç¼ä½ä¸å主è¦åç´çæ¬ï¼æ¯å¹¾åæç¼ä½ä¸åå°çæ¬ã
   
  1.7) æå¾åªè£¡è½å¾å°å° PostgreSQL çæ¯æï¼
  
   PostgreSQL社åéééµä»¶å表çºå¶å¤§å¤æ¸ç¨æ¶æä¾å¹«å©ï¼è¨é±éµä»¶å表ç主ç«é
   »æ¯
   http://www.postgresql.org/community/lists/ï¼ä¸è¬ææ³ä¸ï¼åå å¥General æ
   Bugéµä»¶å表æ¯ä¸åè¼å¥½çéå§ã
   
   主è¦çIRCé »éæ¯å¨FreeNode(irc.freenode.net)ç#postgresqlï¼çºäºé£ä¸æ­
   ¤é »éï¼å¯ä»¥ä½¿ç¨ UNIX ç¨åº ircï¼å¶æä»¤æ ¼å¼ï¼ irc -c '#postgresql'
   "$USER" irc.freenode.net ï¼æè使ç¨å¶ä»IRC客æ¶ç«¯ç¨åºãå¨æ¤ç¶²çµ¡ä¸éå­
   å¨ä¸å PostgreSQL ç西ççé »é(#postgersql-es)åæ³èªé »é
   (#postgresql-fr)ãå樣å°ï¼å¨ EFNET ä¸ä¹æä¸å PostgreSQL ç交æµé »éã
   
   å¯æä¾åæ¥æ¯æçå¬å¸å表å¯å¨ http://techdocs.postgresql.org/companies.php
   ç覽ã
   
  1.8) æå¦ä½æ交ä¸å BUG å ±åï¼
  
   å¯è¨ªå http://www.postgresql.org/support/submitbugï¼å¡«å¯« Bug
   ä¸å ±è¡¨æ ¼å³å¯ï¼å樣ä¹å¯è¨ªå ftp ç«é» ftp://ftp.PostgreSQL.org/pub/
   檢æ¥æç¡æ´æ°çPostgreSQL çæ¬æè£ä¸ã
   
   ééä½¿ç¨ Bug æäº¤è¡¨æ ¼ææ¯ç¼å¾ PostgreSQL éµä»¶å表ç Bug
   é常ææ以ä¸ä¹ä¸åè¦ï¼
     * ææ交å§å®¹ä¸æ¯ä¸å Bug åå¶ä¸æ¯ Bug çåå ã
     * ææ交å§å®¹æ¯ä¸åå·²ç¥ç Bug 並ä¸å·²ç¶å å¥ TODO å¾èçä»»åå表ã
     * ææ交ç Bug å·²å¨ç¶åçæ¬ä¸è¢«ä¿®æ£ã
     * ææ交ç Bug 已修æ£ä½å°æªå°è£ä¸å å¥ç¾å¨çç¼å¸è»é«åã
     * è«æ±æ交èæä¾æ´è©³ç´°çè³è¨ï¼
          + ä½æ¥ç³»çµ±
          + PostgreSQL çæ¬
          + å¯éç¾ Bug ç測試æ¡ä¾
          + 調試è³è¨
          + 調試è·è¹¤è¼¸åº
     * ææ交å§å®¹æ¯ä¸åæ° Bugï¼å°å·è¡ä»¥ä¸å·¥ä½ï¼
          + åµå»ºä¸åæ°è£ä¸ä¸¦å°å¶å å¥ä¸ä¸å主è¦çæ¬ææ¯å°çæ¹é²çæ¬ä¸ã
          + æ¤ Bug æ«æä¸è½ä¿®æ£ï¼å°è¢«å è³ TODO å¾èçä»»åå表ã
       
  1.9) æå¦ä½ç解已ç¥ç BUG ææ«ç¼ºçåè½ï¼
  
   PostgreSQL æ¯æä¸åæ´å±ç SQL:2003 çåéãåé±æåç TODO å表ï¼çè§£å·²ç¥ Bug
   å表ãæ«ç¼ºçåè½åå°ä¾çéç¼è¨åã
   
   è¦æ±å¢å æ°åè½çç³è«é常ææ¶å°ä»¥ä¸ä¹ä¸çåè¦ï¼
     * 該åè½å·²å å¥ TODO å¾èçä»»åå表ã
     * 該åè½ä¸æ¯å¿é çï¼å çºï¼
          + å®æ¯ç¾æçä¸ç¬¦å SQL æ¨æºçæåè½çéè¤ã
          + 該åè½æ§æ大大å¢å 代碼çè¤éç¨åºï¼è帶ä¾ç好èæ¯å¾®ä¸è¶³éçã
          + 該åè½æ¯ä¸å®å¨ææ¯ä¸å¯é çã
     * 該åè½å°è¢«å å¥ TODO å¾èçä»»åå表ã
       
   PostgreSQL ä¸ä½¿ç¨ Bug è·è¹¤ç³»çµ±ï¼å çºæåç¼ç¾å¨éµä»¶å表中
   ç´æ¥åè¦ä»¥åä¿è TODO
   ä»»åå表總æ¯èæ¼ææ°çæçæ¹å¼å·¥ä½æçææ´é«ä¸äºãäºå¯¦ä¸ï¼Bugä¸æå¨æåçè»é«ä¸­
   åå¨å¾é·æéï¼ å°å½±é¿å¾å¤ç¨æ¶çBugä¹ç¸½æ¯å¾å¿«æ被修æ­
   £ãå¯ä¸è½æ¾å°æææ¹é²ãæé«åä¿®æ£çå°æ¹æ¯ CVS
   çæ¥èªè³è¨ï¼å³ä½¿æ¯å¨è»é«æ°çæ¬çç¼å¸è³è¨ä¸ä¹ä¸æååºæ¯ä¸èçè»é«æ´æ°ã
   
  1.10) è½å¤ ç²åçææ°ææªæåªäºï¼
  
   PostgreSQL åå«å¤§éçææªï¼ä¸»è¦æ詳細çåèæåï¼æåé åä¸äºç測試ä¾åãåè¦
   /doc ç®éï¼è¯è¨»ï¼æçº $PGHOME/docï¼ã ä½ éå¯ä»¥å¨ç·ç覽 PostgreSQL
   çæåï¼å¶ç¶²åæ¯ï¼http://www.PostgreSQL.org/docsã
   
   æå©æ¬éæ¼PostgreSQLçæ¸å¨ç·æä¾ï¼å¨
   http://www.postgresql.org/docs/books/awbook.html å
   http://www.commandprompt.com/ppbook/ ã ä¹æ大éç PostgreSQL
   æ¸ç±å¯ä¾è³¼è²·ï¼å¶ä¸æçºæµè¡çä¸æ¬æ¯ç± Korry Douglas 編寫çãå¨
   http://techdocs.PostgreSQL.org/techdocs/bookreviews.phpä¸ ä¸æ大éæé
   PostgreSQL æ¸ç±çç°¡ä»ã å¨ http://techdocs.PostgreSQL.org/ ä¸æ¶éäºæé
   PostgreSQL ç大éæè¡æç« ã
   
   客æ¶ç«¯çå½ä»¤è¡ç¨åºpsqlæä¸äºä»¥ \d éé ­
   çå½ä»¤ï¼å¯é¡¯ç¤ºéæ¼é¡åï¼æä½ç¬¦ï¼å½æ¸ï¼èåçè³è¨ï¼ä½¿ç¨ \?
   å¯ä»¥é¡¯ç¤ºææå¯ç¨çå½ä»¤ã
   
   æåç web ç«é»åå«æ´å¤çææªã
   
  1.11) ææ該æ樣å¸ç¿ SQL ï¼
  
   é¦åèæ®ä¸è¿°æå°çèPostgreSQLç¸éçæ¸ç±ï¼å¦å¤ä¸æ¬æ¯ Teach Yourself SQL in
   21 Days, Second Editionï¼å¶è©³ç´°ä»ç´¹ç網åæ¯
   http://members.tripod.com/er4ebus/sql/index.htmï¼ æåç許å¤ç¨æ¶åæ¡The
   Practical SQL Handbookï¼ Bowman, Judith S.
   編寫ï¼Addison-Wesleyå¬å¸åºçï¼å¶ä»çååæ¡ The Complete Reference SQL,
   Groff 編寫ï¼McGraw-Hill å¬å¸åºçã
   
   å¨ä¸å網åä¸ä¹æå¾å¥½çæç¨ï¼ä»åæ¯
     * http://www.intermedia.net/support/sql/sqltut.shtm
     * http://sqlcourse.com.
     * http://www.w3schools.com/sql/default.asp
     * http://mysite.verizon.net/Graeme_Birchall/id1.html
       
  1.12)å¦ä½æ交è£ä¸ææ¯å å¥éç¼éä¼ï¼
  
   è©³è¦ éç¼äººå¡å¸¸è¦åé¡ (Developer's FAQ) ã
   
  1.13) PostgreSQL åå¶ä»è³æ庫系統æ¯èµ·ä¾å¦ä½ï¼
  
   è©å¹è»é«æ好幾種æ¹æ³ï¼åè½ï¼æ§è½ï¼å¯é æ§ï¼æ¯æåå¹æ ¼ã
   
   åè½
          PostgreSQL ææ大ååç¨è³æ庫æå¤çåè½ï¼ä¾å¦ï¼äºåï¼å­
          æ¥è©¢ï¼è§¸ç¼å¨ï¼è¦åï¼å¤éµåèå®æ´æ§åè¤éçéå®çã
          æåéæä¸äºå®åæ²æçç¹æ§ï¼å¦ç¨æ¶å®ç¾©é¡åï¼ç¹¼æ¿ï¼è¦ååå¤çæ¬ä¸¦è¡æ§å¶ä
          »¥æ¸å°éççç¨çã
          
   æ§è½
          PostgreSQLåå¶ä»åç¨åéæºçè³æ庫å·æé¡ä¼¼çæ§è½ãå°æäºèçå®æ¯è¼å¿«ï¼å°
          å¶ä»ä¸äºèçå®æ¯è¼æ¢ã èå¶ä»è³æ庫ç¸æ¯ï¼æåçæ§è½åªå£éå¸¸å¨ +/-
          10%ä¹éã
          
   å¯é æ§
          æåé½ç¥éè³æ庫å¿é æ¯å¯é çï¼å¦åå®å°±ä¸é»ç¨é½æ²æãæååªååå°ç¼ä½ç¶éèª
          ç測試çï¼ç¼ºé·æå°çç©©å®ä»£ç¢¼ãæ¯åçæ¬è³å°æä¸åæç beta
          測試æéï¼ä¸¦ä¸æåçç¼å¸æ­
          ·å²é¡¯ç¤ºæåå¯ä»¥æä¾ç©©å®çï¼ç¢åºçï¼å¯ç¨æ¼çç¢ä½¿ç¨ççæ¬ãæåç¸ä¿¡å¨é
          æ¹é¢æåèå¶ä»çè³æ庫è»é«æ¯ç¸ç¶çã
          
   æ¯æ
          æåçéµä»¶å表æä¾ä¸åé常大çéç¼äººå¡åç¨æ¶ççµä»¥å¹«å©è§£æ±ºæ碰å°ç
          ä»»ä½åé¡ãæåä¸è½ä¿è­
          總æ¯è½è§£æ±ºåé¡ï¼ç¸æ¯ä¹ä¸ï¼åç¨è³æ庫è»é«ä¹ä¸¦ä¸æ¯ç¸½è½å¤ æä¾è§
          £æ±ºæ¹æ³ã
          ç´æ¥èéç¼äººå¡ï¼ç¨æ¶ç¾¤ï¼æååæºç¨åºæ¥è§¸ä½¿PostgreSQLçæ¯ææ¯å¶ä»è³
          æ庫éè¦å¥½ãéæä¸äºå業
          æ§çå¨é¢æè¡æ¯æï¼å¯ä»¥çµ¦æä¾çµ¦é£äºéè¦ç人ãï¼åé±1.7 å°ç¯ï¼
          
   å¹æ ¼
          æåå°ä»»ä½ç¨éé½åè²»ï¼åæ¬åç¨åéåç¨ç®çã
          ä½ å¯ä»¥ä¸å éå¶å°åä½ çç¢å裡å å¥æåç代碼ï¼é¤äºé£äºæåå¨ä¸é¢ççæ¬
          è²æ裡è²æç BSDçæ¬ä¹å¤çå§å®¹ã
          
  1.14) PostgreSQL å¯ä»¥èçæè¿ååå家å¤æå¶çè®åå?
  
   PostgreSQL 8.0ä¹åççæ¬æ¯ä½¿ç¨ä½æ¥ç³»çµ±ä¸çæåè³æ庫ä¾èçå¤æå¶çè³è¨ï¼èª
   8.0 çå以å¾ççæ¬ PostgreSQL æèªèº«å«æææ°çæåè³è¨ã
     _________________________________________________________________
   
ç¨æ¶å®¢æ¶ç«¯åé¡

  2.1) æåå¯ä»¥ç¨ä»éº¼èªè¨å PostgreSQL é²è¡æºéï¼
  
   PostgreSQL (é è¨ææ³)åªå®è£æ C åå§åµå¼ C
   çæ¥å£ï¼å¶ä»çæ¥å£é½æ¯ç¨ç«çé ç®ï¼è½å¤ åå¥ä¸è¼ï¼éäºæ¥å£é ç®ç¨ç«ç好è
   æ¯ä»åå¯ä»¥æåèªçç¼å¸è¨åååèªç¨ç«çéç¼çµã
   
   ä¸äºç·¨ç¨èªè¨å¦ PHP é½æ訪å PostgreSQL çæ¥å£ï¼PerlãTCLãPython
   以åå¾å¤å¶ä»èªè¨çæ¥å£å¨ http://gborg.postgresql.org 網ç«ä¸ç
   Drivers/Interfaces å°ç¯å¯æ¾å°ï¼ 並ä¸éé Internet å¾å®¹ææç´¢å°ã
   
  2.2) æä»éº¼å·¥å·å¯ä»¥æ PostgreSQL ç¨æ¼ Web é é¢ï¼
  
   ä¸åä»ç´¹ä»¥è³æ庫çºå¾å°çæºä¸é¯çç«é»æ¯ï¼http://www.webreview.comã
   
   å°æ¼ Web éæï¼PHP æ¯ä¸å極好çæ¥å£ãå®å¨ http://www.php.net/ã
   
   å°æ¼è¤éçä»»åï¼å¾å¤äººæ¡ç¨ Perl æ¥å£å ä½¿ç¨ CGI.pm ç DBD::Pg æ mod_perl
   ã
   
  2.3)PostgreSQL ææåå½¢ç¨æ¶çé¢åï¼
  
   åæ¥ç¨æ¶ææ¯éæºéç¼äººå¡è½æ¾å°å¾å¤çæé PostgreSQLçGUI å形工å·è»é«ï¼å¨
   PostgreSQL社åææª æä¸å詳細çå表ã
     _________________________________________________________________
   
系統管çåé¡

  3.1)ææ樣è½æ PostgreSQL è£å¨ /usr/local/pgsql 以å¤çå°æ¹ï¼
  
   å¨éè¡ configure æå ä¸ --prefix é¸é ã
   
  3.2) æå¦ä½æ§å¶ä¾èªå¶ä»é»è¦çé£æ¥ï¼
  
   é è¨ææ³ä¸ï¼PostgreSQL åªå許ä¾èªæ¬æ©ä¸éé unix åå¥æ¥åæ TCP/IP
   æ¹å¼çé£æ¥ã ä½ åªæå¨ä¿®æ¹äºéç½®æ件 postgresql.conf ä¸ç
   listen_addressesï¼ä¸ä¹å¨éç½®æ件 $PGDATA/pg_hba.conf ä¸æéäº
   åºæ¼é ç¨é»è¦ï¼ host-based ï¼ç身份èªèï¼ä¸¦éæ°åå
   PostgreSQLï¼å¦åå¶ä»é»è¦æ¯ä¸è½èä½ ç PostgreSQL 伺æå¨é²è¡é£æ¥çã
   
  3.3) ææ樣調æ´è³æ庫å¼æ以ç²å¾æ´å¥½çæ§è½ï¼
  
   æä¸å主è¦æ¹é¢å¯ä»¥æå PostgreSQL çæ½è½ã
   
   æ¥è©¢æ¹å¼çè®å
          é主è¦æ¶åä¿®æ¹æ¥è©¢æ¹å¼ä»¥ç²åæ´å¥½çæ§è½:
          
          + åµå»ºç´¢å¼ï¼åæ¬è¡¨éå¼åé¨åç´¢å¼ï¼
          + ä½¿ç¨ COPY èªå¥ä»£æ¿å¤å Insert èªå¥ï¼
          + å°å¤åSQLèªå¥çµæä¸åäºå以æ¸å°æ交äºåçéé·ï¼
          + å¾ä¸åç´¢å¼ä¸æåå¤æ¢è¨éæä½¿ç¨ CLUSTERï¼
          + å¾ä¸åæ¥è©¢çµæä¸ååºé¨åè¨éæä½¿ç¨ LIMITï¼
          + 使ç¨é ç·¨è¯å¼æ¥è©¢ï¼Prepared Query)ï¼
          + ä½¿ç¨ ANALYZE 以ä¿æ精確çåªåçµ±è¨ï¼
          + å®æä½¿ç¨ VACUUM æ pg_autovacuum
          + é²è¡å¤§éè³ææ´æ¹æååªé¤ç´¢å¼ï¼ç¶å¾é建索å¼ï¼
            
   伺æå¨çéç½®
          éç½®æ件 postgres.conf ä¸çå¾å¤è¨­
          ç½®é½æå½±é¿æ§è½ï¼ææåæ¸çå表å¯è¦ï¼
          管çå¡æå/è³æ庫伺æå¨éè¡ç°å¢/è³æ庫伺æå¨éè¡éç½®ï¼
          æéåæ¸ç解éå¯è¦ï¼http://www.varlena.com/varlena/GeneralBits/Tidb
          its/annotated_conf_e.html å
          http://www.varlena.com/varlena/GeneralBits/Tidbits/perf.htmlã
          
   硬é«çé¸æ
          é»è¦ç¡¬é«å°æ§è½çå½±é¿å¯ç覽
          http://candle.pha.pa.us/main/writings/pgsql/hw_performance/inde
          x.html å http://www.powerpostgresql.com/PerfList/ã
          
  3.4)PostgreSQL 裡å¯ä»¥ç²å¾ä»éº¼æ¨£ç調試ç¹æ§ï¼
  
   PostgreSQL æå¾å¤é¡ä¼¼ log_*
   ç伺æå¨éç½®è®éå¯ç¨æ¼æ¥è©¢çåå°åé²ç¨çµ±è¨ï¼èéäºå·¥ä½å°èª¿è©¦åæ§è½æ¸¬è©¦å
   ¾æ幫å©ã
   
  3.5) çºä»éº¼å¨è©¦åé£æ¥ææ¶å°ãSorry, too many
  clientsï¼å·²æ太å¤ç¨æ¶é£æ¥ï¼ãæ¶æ¯ï¼
  
   éè¡¨ç¤ºä½ å·²éå°é è¨ 100 å並ç¼(åä½)å¾å°é²ç¨æ¸çéå¶ï¼ä½ éè¦ééä¿®æ¹
   postgresql.conf æ件ä¸ç max_connections å¼ä¾ å¢å  postmaster
   çå¾å°ä½µç¼èçæ¸ï¼ä¿®æ¹å¾ééæ°åå postmasterã
   
  3.6)PostgreSQL çåç´éç¨æåªäºå§å®¹ ï¼
  
   PostgreSQL éç¼çµå°æ¯æ¬¡å°çæ¬çåç´ä¸»è¦åªåäºä¸äº Bug ä¿®æ£å·¥ä½ï¼å æ¤å¾
   7.4.8 åç´å° 7.4.9 ä¸éè¦ dump å restoreï¼åéè¦åæ­
   ¢è³æ庫伺æå¨ï¼å®è£æ´æ°å¾çè»é«åï¼ç¶å¾éå伺æå¨å³å¯ã
   
   ææPostgreSQLçç¨æ¶æ該å¨ææ¥è¿ï¼ä½ æ使ç¨ç主çæ¬ï¼çå°æ¹é²çæ¬ç¼ä½ç¡å¿«åç´
   ãå管æ¯æ¬¡åç´å¯è½é½æä¸é»é¢¨éªï¼PostgreSQLçå°æ¹ é²çååæ¯è¨è¨ç¨ä¾ä¿®æ­
   £ä¸äº Bug
   çï¼ç¨å¼ç¢¼æ¹åè¼å°ï¼æ以風éªéæ¯å¾å°çãPostgreSQL社åèªçºä¸è¬ææ³ä¸ä¸åç´ç
   風éªéæ¯å¤æ¼åç´çã
   
   主çæ¬çåç´ï¼ä¾å¦å¾ 7.3 å° 7.4ï¼é常æä¿®æ¹ç³»çµ±è¡¨åè³æ表çå§é¨æ ¼å¼ã
   éäºæ¹è®ä¸è¬æ¯è¼è¤éï¼å æ¤æåä¸ç¶æè³ææ件çåå¾å¼å®¹æ§ãå æ¤å¾èçæ¬ä¸­
   é²è¡è³æå°åºï¼dumpï¼/ç¶å¾å¨æ°çæ¬ä¸­
   é²è¡è³æå°å¥ï¼reloadï¼å°ä¸»çæ¬çåç´æ¯å¿é çã
   
  3.7)(ä½¿ç¨ PostgreSQL )æéè¦ä½¿ç¨ä»éº¼é»è¦ç¡¬é« ï¼
  
   ç±æ¼é»è¦ç¡¬é«å¤§å¤æ¸æ¯ç¸å®¹çï¼äººå總æ¯å¾åæ¼ç¸ä¿¡ææé»è¦ç¡¬é«è³ªéä¹æ¯ç¸
   åçãäºå¯¦ä¸ä¸æ¯ï¼ ECC RAMï¼å¸¶å¥å¶æ ¡é©çè¨æ¶é«ï¼ï¼SCSI
   ï¼ç¡¬ç¢ï¼ååªè³ªç主æ©æ¿æ¯ä¸äºä¾¿å®è²¨è¦æ´å å¯é ä¸å·ææ´å¥½çæ§è½ã
   PostgreSQL å¹¾ä¹å¯ä»¥éè¡å¨ä»»ä½ç¡¬é«ä¸ï¼
   ä½å¦æå¯é æ§åæ§è½å°ä½ ç系統å¾éè¦ï¼ä½ å°±éè¦å¨é¢çç 究ä¸ä¸ä½ ç硬é«çµæ
   äºãå¨æåçéµä»¶å表ä¸ä¹æéæ¼ ç¡¬é«éç½®åæ§å¹æ¯çè¨è«ã
     _________________________________________________________________
   
æä½åé¡

  4.1) å¦ä½åªé¸æä¸åæ¥è©¢çµæçé å¹¾è¡ï¼ææ¯é¨æ©çä¸è¡ï¼
  
   å¦æä½ åªæ¯è¦æåå¹¾è¡è³æï¼ä¸¦ä¸ä½ å¨å·è¡æ¥è©¢ä¸­
   ç¥é確åçè¡æ¸ï¼ä½ å¯ä»¥ä½¿ç¨ LIMIT åè½ã å¦ææä¸åç´¢å¼è ORDER BY 中
   çæ¢ä»¶å¹éï¼PostgreSQL å¯è½å°±åªèçè¦æ±çé å¹¾æ¢è¨éï¼
   ï¼å¦åå°å°æ´åæ¥è©¢é²è¡èçç´å°çæéè¦çè¡ï¼ãå¦æå¨å·è¡æ¥è©¢åè½æä¸ç¥é確åçè¨éæ
   ¸ï¼ å¯ä½¿ç¨æ¸¸æ¨(cursor)åFETCHåè½ã
   
   å¯ä½¿ç¨ä»¥ä¸æ¹æ³æåä¸è¡é¨æ©è¨éçï¼
       SELECT  cols
      FROM tab
      ORDER BY random()
      LIMIT 1 ;

  4.2)
  å¦ä½æ¥ç表ãç´¢å¼ãè³æ庫以åç¨æ¶çå®ç¾©ï¼å¦ä½æ¥çpsql裡ç¨å°çæ¥è©¢æ令並顯示å
  ®åï¼
  
   å¨psqlä¸ä½¿ç¨ \dt å½ä»¤ä¾é¡¯ç¤ºè³æ表çå®ç¾©ï¼è¦ç解 psql 中
   çå®æ´å½ä»¤å表å¯ä½¿ç¨ \? ï¼å¦å¤ï¼ä½ ä¹å¯ä»¥é±è® psql çæºä»£ç¢¼ æ件
   pgsql/src/bin/psql/describe.cï¼å®åæ¬çºçæ psql åææ§å½ä»¤ç輸åºçææ SQL
   å½ä»¤ãä½ éå¯ä»¥å¸¶ -E é¸é åå psqlï¼ é樣å®å°åå°åºä½ å¨ psql 中
   æ給åºçå½ä»¤å·è¡æçå§é¨å¯¦é使ç¨ç SQL
   æ¥è©¢èªå¥ãPostgreSQLä¹æä¾äºä¸åå¼å®¹ SQLç INFORMATION SCHEMA æ¥å£ï¼
   ä½ å¯ä»¥å¾é裡ç²åéæ¼è³æ庫çè³è¨ã
   
   å¨ç³»çµ±ä¸ä¹æä¸äºä»¥ pg_ æé ç系統表ä¹æè¿°äºè¡¨çå®ç¾©ã
   
   ä½¿ç¨ psql -l æ令å¯ä»¥ååºææçè³æ庫ã
   
   ä¹å¯ä»¥ç覽ä¸ä¸ pgsql/src/tutorial/syscat.source
   æ件ï¼å®åèäºå¾å¤å¯å¾è³æ庫系統表ä¸ç²åè³è¨çSELECTèªæ³ã
   
  4.3) å¦ä½æ´æ¹ä¸åæ¬ä½çè³æé¡åï¼
  
   å¨8.0çæ¬è£¡æ´æ¹ä¸åæ¬ä½çè³æé¡åå¾å®¹æï¼å¯ä½¿ç¨ ALTER TABLE ALTER COLUMN
   TYPE ã
   
   å¨ä»¥åççæ¬ä¸ï¼å¯ä»¥é樣åï¼
    BEGIN;
    ALTER TABLE tab ADD COLUMN new_col new_data_type;
    UPDATE tab SET new_col = CAST(old_col AS new_data_type);
    ALTER TABLE tab DROP COLUMN old_col;
    COMMIT;

   ä½ ç¶å¾å¯ä»¥ä½¿ç¨ VACUUM FULL tab æ令ä¾ä½¿ç³»çµ±æ¶åç¡æè³ææä½ç¨ç空éã
   
  4.4) å®æ¢è¨éï¼å®å表ï¼å®åè³æ庫çæ大éå¶æ¯å¤å°ï¼
  
   ä¸é¢æ¯ä¸äºéå¶ï¼
   
     å®åè³æ庫æå¤§å°ºå¯¸ï¼    ç¡éå¶ï¼å·²åå¨æ 32TB çè³æ庫ï¼
     å®å表çæå¤§å°ºå¯¸ï¼      32 TB
     ä¸è¡è¨éçæå¤§å°ºå¯¸ï¼     1.6 TB
     ä¸åæ¬ä½çæ大尺寸?      1 GB
     ä¸å表裡æ大åæ¸ï¼       ç¡éå¶
     ä¸å表裡æ大æ¬ä½æ¸ï¼    250-1600 ï¼èåé¡åæéï¼
     ä¸å表裡çæ大索å¼æ¸éï¼ ç¡éå¶
   
   ç¶ç¶ï¼å¯¦éä¸æ²æçæ£çç¡éå¶ï¼éæ¯è¦åå¯ç¨ç£ç¤ç©ºéãå¯ç¨è¨æ¶é«/交æåçå¶ç´ã
   äºå¯¦ä¸ï¼ç¶ä¸è¿°éäºæ¸å¼è®å¾ç°å¸¸å°å¤§æï¼ç³»çµ±æ§è½ä¹æåå¾å¤§å½±é¿ã
   
   å®è¡¨çæå¤§å¤§å° 32 TB ä¸éè¦ä½æ¥­
   系統å°å®åæ件ä¹éé麼大çæ¯æã大表ç¨å¤å 1 GB çæ件åå²ï¼å æ­
   ¤æ件系統大å°çéå¶æ¯ä¸éè¦çã
   
   å¦æé è¨çå¡å¤§å°å¢é·å° 32K ï¼æ大çå®è¡¨å¤§å°åæ大åæ¸éå¯ä»¥å¢å å°ååã
   
   æä¸åéå¶å°±æ¯ä¸è½å°å¤§å°å¤æ¼2000å­
   ç¯çååµå»ºç´¢å¼ã幸éå°æ¯é樣çç´¢å¼å¾å°ç¨å°ãééå°å¤å­
   ç¯åçå§å®¹é²è¡MD5åç¨éç®çµæé²è¡å½æ¸ç´¢å¼å¯å°åçå¯ä¸æ§å¾å°ä¿èï¼
   並ä¸å¨æ檢索å許å°åä¸çå®è©é²è¡æç´¢ã
   
  4.5) åå²ä¸åå¸åçææ¬æ件裡çè³æéè¦å¤å°ç£ç¤ç©ºéï¼
  
   ä¸å Postgres è³æ庫ï¼å­
   å²ä¸åææ¬æ件ï¼æä½ç¨ç空éæå¤å¯è½éè¦ç¸ç¶æ¼éåææ¬æ件èªèº«å¤§å°5åçç£ç¤ç©ºé
   ã
   
   ä¾å¦ï¼åè¨æä¸å 100,000 è¡çæ件ï¼æ¯è¡æä¸åæ´æ¸åä¸åææ¬æè¿°ã å設
   ææ¬ä¸²çå¹³åé·åº¦çº20ä½åçµ(Byte)ãææ¬æ件ä½ç¨ 2.8 MBãå­
   æ¾éäºè³æçPostgreSQLè³æ庫æ件大ç´æ¯ 5.2 MB:
     24 ååçµ: æ¯è¡çé ï¼å¤§ç´å¼ï¼
     24 ååçµç¯: ä¸åæ´æ¸åæ¬ä½åä¸åææ¬åæ¬ä½
   +  4 ååçµç¯: é é¢å§æååçµçæé
   ----------------------------------------
     52 ååçµæ¯è¡

   PostgreSQL è³æé ç大å°æ¯ 8192 ä½åçµ (8 KB)ï¼åï¼

   8192 ååçµæ¯é
   -------------------   =  158 è¡/è³æé ï¼åä¸åæ´ï¼
     52 ååçµæ¯è¡

   100000 è³æè¡
   --------------------  =  633 è³æé ï¼åä¸åæ´ï¼
      146 è¡/è³æé

   633 è³æé  * 8192 åç¯/é   = 5,185,536 åç¯ï¼5.2 MBï¼

   ç´¢å¼ä¸éè¦é麼å¤çé¡å¤æ¶èï¼ä½ä¹ç¢ºå¯¦åæ¬è¢«ç´¢å¼çè³æï¼å æ­
   ¤å®åä¹å¯è½å¾å¤§ã
   
   ç©ºå¼ NULL åæ¾å¨ä½åä¸ï¼å æ¤ä½ç¨å¾å°ç空éã
   
  4.6) çºä»éº¼æçæ¥è©¢å¾æ¢ï¼çºä»éº¼éäºæ¥è©¢æ²æå©ç¨ç´¢å¼ï¼
  
   並éæ¯åæ¥è©¢é½æèªå使ç¨ç´¢å¼ãåªæå¨è¡¨ç大å°è¶éä¸åæå°å¼ï¼ä¸¦ä¸æ¥è©¢åªæé
   ¸ä¸è¡¨ä¸è¼å°æ¯ä¾çè¨éææææ¡ç¨ç´¢å¼ã éæ¯å çºç´¢å¼æçå¼èµ·çé¨å³ç£ç¤å­
   åå¯è½æ¯ç´æ¥å°è®å表ï¼é åºæçï¼æ´æ¢ã
   
   çºäºå¤æ·æ¯å¦ä½¿ç¨ç´¢å¼ï¼PostgreSQL
   å¿é ç²å¾æé表ççµ±è¨å¼ãéäºçµ±è¨å¼å¯ä»¥ä½¿ç¨ VACUUM ANALYZEï¼æ ANALYZE
   ç²å¾ã 使ç¨çµ±è¨å¼ï¼åªåå¨ç¥é表中
   æå¤å°è¡ï¼å°±è½å¤ æ´å¥½å°å¤æ·æ¯å¦å©ç¨ç´¢å¼ã
   çµ±è¨å¼å°ç¢ºå®åªåçé£æ¥é åºåé£æ¥æ¹æ³ä¹å¾æç¨ãå¨è¡¨çå§å®¹ç¼çè®åæï¼æå®æé²è
   ¡çµ±è¨å¼çæ´æ°æ¶éã
   
   ç´¢å¼é常ä¸ç¨æ¼ ORDER BY
   æå·è¡é£æ¥ãå°ä¸å大表çä¸æ¬¡é åºæçååä¸æ¬¡æåºé常æ¯ç´¢å¼æçè¦å¿«ãç¶èï¼å¦æ
   å° LIMIT å ORDER BY
   çµåå¨ä¸èµ·ä½¿ç¨ç話ï¼é常å°æ使ç¨ç´¢å¼ï¼å çºéæåè¿å表ä¸çä¸å°é¨åè¨éã
   
   å¦æä½ ç¢ºä¿¡PostgreSQLçåªåå¨ä½¿ç¨é åºæçæ¯ä¸æ£ç¢ºçï¼ä½ å¯ä»¥ä½¿ç¨SET
   enable_seqscan TO 'off'æ令ä¾ééé åºæçï¼
   ç¶å¾å次éè¡æ¥è©¢ï¼ä½ å°±å¯ä»¥çåºä½¿ç¨ä¸åç´¢å¼æçæ¯å¦ç¢ºå¯¦è¦å¿«ä¸äºã
   
   ç¶ä½¿ç¨éé符æä½ï¼ä¾å¦ LIKE æ ~ æï¼ç´¢å¼åªè½å¨ç¹å®çææ³ä¸ä½¿ç¨ï¼
     * å符串çéå§é¨åå¿é æ¯æ®éå符串ï¼ä¹å°±æ¯èªªï¼
          + LIKE 模å¼ä¸è½ä»¥ % æé ã
          + ~ ï¼æ£å表éå¼ï¼æ¨¡å¼å¿é 以 ^ æé ã
     * å符串ä¸è½ä»¥å¹éå¤åå符ç模å¼é¡æé ï¼ä¾å¦ [a-e]ã
     * 大å°å¯«ç¡éçæ¥æ¾ï¼å¦ ILIKE å ~* çä¸ä½¿ç¨ç´¢å¼ï¼ä½å¯ä»¥ç¨ 4.8
       ç¯æè¿°ç表éå¼ç´¢å¼ã
     * å¨å initdb æå¿é æ¡ç¨é è¨çæ¬å°è¨ç½® C
       localeï¼å çºç³»çµ±ä¸å¯è½ç¥éå¨é C locale ææ³æä¸ä¸åæ大å符æ¯ä»éº¼ã
       å¨é種ææ³ä¸ï¼ä½ å¯ä»¥åµå»ºä¸åç¹æ®ç text_pattern_ops ç´¢å¼ä¾ç¨æ¼
       LIKE çç´¢å¼ã
       
   å¨ 8.0 ä¹åççæ¬ä¸­
   ï¼é¤éè¦æ¥è©¢çè³æé¡ååç´¢å¼çè³æé¡åç¸å¹éï¼å¦åç´¢å¼ç¶å¸¸æ¯æªè¢«ç¨å°ï¼ç¹å¥æ
   ¯å° int2, int8 åæ¸å¼åçç´¢å¼ã
   
  4.7) æå¦ä½æè½çå°æ¥è©¢åªåå¨æ¯æ樣è©ä¼°èçæçæ¥è©¢ï¼
  
   åè EXPLAIN æåé ã
   
  4.8) ææ樣åæ£å表éå¼æç´¢å大å°å¯«ç¡éçæ­
  £å表éå¼æ¥æ¾ï¼æ樣å©ç¨ç´¢å¼é²è¡å¤§å°å¯«ç¡éæ¥æ¾ï¼
  
   æä½ç¬¦ ~ èçæ£å表éå¼å¹éï¼è ~* èç大å°å¯«ç¡éçæ£å表éå¼å¹éã大å°å¯«ç¡éç
   LIKE è®ç¨®æçº ILIKEã
   
   大å°å¯«ç¡éççå¼æ¯è¼é常寫åï¼
    SELECT *
    FROM tab
    WHERE lower(col) = 'abc';

   é樣å°ä¸æ使ç¨æ¨æºçç´¢å¼ãä½æ¯å¯ä»¥åµå»ºä¸åå¨é種ææ³ä¸ä½¿ç¨ç表éå¼ç´¢å¼
   :
    CREATE INDEX tabindex ON tab (lower(col));

   å¦æä¸è¿°ç´¢å¼å¨åµå»ºæå å¥ UNIQUE ç´æï¼éç¶ç´¢å¼æ¬ä½èªèº«å§å®¹å¯ä»¥å­
   å²å¤§å°å¯«ä¸éçå§å®¹ï¼ä½å¦ææ UNIQUE
   ç´æå¾ï¼éäºå§å®¹ä¸è½ååæ¯å¤§å°å¯«ä¸åï¼å¦åæé æè¡çªï¼ãçºäºä¿è­
   ä¸ç¼çé種ææ³ï¼å¯ä»¥ä½¿ç¨ CHECK ç´ææ¢ä»¶ææ¯è§¸ç¼å¨å¨éå¥æé²è¡éå¶ã
   
  4.9) å¨ä¸åæ¥è©¢è£¡ï¼ææ樣檢測ä¸åæ¬ä½æ¯å¦çº NULL
  ï¼æå¦ä½æè½æºç¢ºæåºèä¸è«ææ¬ä½æ¯å¦å« NULL å¼ï¼
  
   ç¨ IS NULL å IS NOT NULL 測試éåæ¬ä½ï¼å·é«æ¹æ³å¦ä¸ï¼
   SELECT *
   FROM tab
   WHERE col IS NULL;

   çºäºè½å°å« NULL æ¬ä½æåºï¼å¯å¨ ORDER BY æ¢ä»¶ä¸ä½¿ç¨ IS NULL å IS NOT
   NULL 修飾符ï¼æ¢ä»¶çºç true å°æ¯æ¢ä»¶çºå false æå¨åé¢ï¼ä¸é¢çä¾å­
   å°±æå°å« NULL çè¨éæå¨çµæçä¸é¢é¨åï¼
   SELECT *
   FROM tab
   ORDER BY (col IS NOT NULL)

  4.10) å種å符é¡åä¹éæä»éº¼ä¸åï¼
  
   é¡å å§é¨å稱 說æ
   VARCHAR(n) varchar æå®äºæ大é·åº¦ï¼è®é·å­
   符串ï¼ä¸è¶³å®ç¾©é·åº¦çé¨åä¸è£é½
   CHAR(n) bpchar å®é·å符串ï¼å¯¦éè³æä¸è¶³å®ç¾©é·åº¦æï¼ä»¥ç©ºæ ¼è£é½
   TEXT text æ²æç¹å¥çä¸ééå¶ï¼ååè¡çæ大é·åº¦éå¶ï¼
   BYTEA bytea è®é·åç¯åºåï¼ä½¿ç¨NULLå符ä¹æ¯å許çï¼
   "char" char å®åå符
   
   å¨ç³»çµ±è¡¨åå¨ä¸äºé¯èª¤è³è¨è£¡ä½ å°çå°å§é¨å稱ã
   
   ä¸é¢æåçåå種é¡åæ¯ "varlena"ï¼è®é·ï¼é¡åï¼ä¹å°±æ¯èªªï¼éé çååå­
   ç¯æ¯é·åº¦ï¼å¾é¢ææ¯è³æï¼ã æ¼æ¯å¯¦éä½ç¨ç空éæ¯è²æç大å°è¦å¤ä¸äºã
   ç¶èéäºé¡åå¦å®ç¾©å¾é·æé½å¯ä»¥è¢«å£ç¸®åå²ï¼å æ­
   ¤ç£ç¤ç©ºéä¹å¯è½æ¯é æ³çè¦å°ã
   
   VARCHAR(n) å¨åå²éå¶äºæ大é·åº¦çè®é·å符串æ¯æ好çã TEXT é©ç¨æ¼å­
   å²æ大å¯é 1G å·¦å³ä½æªå®ç¾©éå¶é·åº¦çå符串ã
   
   CHAR(n) æé©åæ¼åå²é·åº¦ç¸åçå符串ã
   CHAR(n)ææ ¹ææ給å®çæ¬ä½é·åº¦ä»¥ç©ºæ ¼è£è¶³ï¼ä¸è¶³çæ¬ä½å§å®¹ï¼ï¼ è
   VARCHAR(n) åªåå²æ給å®çè³æå§å®¹ã BYTEA ç¨æ¼åå²äºé²å¶è³æï¼å°¤å¶æ¯åå«
   NULL åç¯çå¼ãéäºé¡åå·æå·®ä¸å¤çæ§è½ã
   
  4.11.1) ææ樣åµå»ºä¸ååºåèææ¯èªåéå¢çæ¬ä½ï¼
  
   PostgreSQL æ¯æ SERIAL
   è³æé¡åãï¼æ¬ä½å®ç¾©çºSERIALå¾ï¼å°èªååµå»ºä¸ååºåçæå¨ï¼ä¾å¦ï¼
   CREATE TABLE person (
      id   SERIAL,
      name TEXT
   );

   æèªåè½æçºä»¥ä¸SQLèªå¥ï¼
   CREATE SEQUENCE person_id_seq;
   CREATE TABLE person (
      id   INT4 NOT NULL DEFAULT nextval('person_id_seq'),
      name TEXT
   );

   åè create_sequence æåé ç²åéæ¼åºåçæå¨çæ´å¤è³è¨ã
   
  4.11.2) æå¦ä½ç²å¾ä¸åæå¥çåºåèçå¼ï¼
  
   ä¸ç¨®æ¹æ³æ¯å¨æå¥ä¹ååç¨å½æ¸ nextval() å¾åºåå°è±¡è£¡æª¢ç´¢åºä¸ä¸å SERIAL
   å¼ï¼ç¶å¾åç¨æ¤å¼ç²¾ç¢ºå°æå¥ãä½¿ç¨ 4.11.1 裡çä¾è¡¨ï¼å¯ç¨å½ç¢¼é樣æè¿°ï¼
   new_id = execute("SELECT nextval('person_id_seq')");
   execute("INSERT INTO person (id, name) VALUES (new_id, 'Blaise Pascal')");

   é樣éè½å¨å¶ä»æ¥è©¢ä¸ä½¿ç¨åæ¾å¨ new_id 裡çæ°å¼ï¼ä¾å¦ï¼ä½çºåç§ person
   表çå¤éµï¼ã 注æèªååµå»ºç SEQUENCE å°è±¡çå稱å°ææ¯
   <table>_<serialcolumn>_seqï¼ é裡 table å serialcolumn
   åå¥æ¯ä½ ç表çå稱åä½ ç SERIAL æ¬ä½çå稱ã
   
   é¡ä¼¼çï¼å¨ SERIAL å°è±¡é è¨æå¥å¾ä½ å¯ä»¥ç¨å½æ¸ currval() 檢索å賦å¼ç
   SERIAL å¼ï¼ä¾å¦ï¼
   execute("INSERT INTO person (name) VALUES ('Blaise Pascal')");
   new_id = execute("SELECT currval('person_id_seq')");

  4.11.3) åæä½¿ç¨ currval() æå°è´åå¶ä»ç¨æ¶çè¡çªææ³åï¼
  
   ä¸æãcurrval() è¿åçæ¯ä½ æ¬æ¬¡æ話é²ç¨æ賦çå¼èä¸æ¯ææç¨æ¶çç¶åå¼ã
   
  4.11.4) çºä»éº¼ä¸å¨äºåç°å¸¸ä¸æ¢å¾éç¨åºåèå¢ï¼çºä»éº¼å¨åºåèæ¬ä½çåå¼ä¸åå¨éæ·å¢ï¼
  
   çºäºæé«ä½µç¼æ§ï¼åºåèå¨éè¦çæå賦äºæ­
   £å¨éè¡çäºåï¼ä¸¦ä¸å¨äºåçµæä¹åä¸é²è¡éå®ï¼ éå°±æå°è´ç°å¸¸ä¸­
   æ¢çäºåå¾ï¼åºåèæåºç¾ééã
   
  4.12) ä»éº¼æ¯ OID ï¼ä»éº¼æ¯ CTID ï¼
  
   PostgreSQL 裡åµå»ºçæ¯ä¸è¡è¨éé½æç²å¾ä¸åå¯ä¸ç OIDï¼é¤éå¨åµå»ºè¡¨æ使ç¨
   WITHOUT OIDS é¸é ã OID åµå»ºææèªåçæä¸å 4ä½åçµçæ´æ¸ï¼ææ OID å¨ç¸æ
   PostgreSQL 伺æå¨ä¸åæ¯å¯ä¸çã ç¶èï¼å®å¨è¶é 40åæå°æº¢åºï¼ OID æ­
   ¤å¾æåºç¾éè¤ãPostgreSQL å¨å®çå§é¨ç³»çµ±è¡¨è£¡ä½¿ç¨ OID
   å¨è¡¨ä¹é建ç«è¯ç¹«ã
   
   å¨ç¨æ¶çè³æ表ä¸ï¼æ好æ¯ä½¿ç¨ SERIAl ä¾ä»£æ¿ OID å çº SERIAL åªè¦ä¿è­
   å¨å®å表ä¸çæ¸å¼æ¯å¯ä¸çå°±å¯ä»¥äºï¼é樣å®æº¢åºçå¯è½æ§å°±é常å°äºï¼
   SERIAL8 å¯ç¨ä¾ä¿å8ååçµçåºåæ¸å¼ã
   
   CTID ç¨æ¼æ¨è帶èè³æå¡ï¼å°åï¼åï¼å¡å§ï¼å移çç¹å®çç©çè¡ã CTID
   å¨è¨é被æ´æ¹æéè¼å¾ç¼çæ¹è®ãç´¢å¼è³æ使ç¨å®åæåç©çè¡ã
   
  4.13) çºä»éº¼ææ¶å°é¯èª¤è³è¨ãERROR: Memory exhausted in AllocSetAlloc()ãï¼
  
   éå¾å¯è½æ¯ç³»çµ±çèæ¬å§åç¨åäºï¼æèå§æ ¸å°æäºè³æºæè¼ä½çéå¶å¼ãå¨åå
   postmaster ä¹å試試ä¸é¢çå½ä»¤ï¼
   ulimit -d 262144
   limit datasize 256m

   å決æ¼ä½ ç¨ç
   shellï¼ä¸é¢å½ä»¤åªæä¸æ¢è½æåï¼ä½æ¯å®å°æä½ çé²ç¨è³æ段éå¶è¨å¾æ¯è¼é«ï¼
   å èä¹è¨±è½è®æ¥è©¢å®æãéæ¢å½ä»¤æç¨æ¼ç¶åé²ç¨ï¼ä»¥åææå¨éæ¢å½ä»¤éè¡å¾åµå»ºç
   åé²ç¨ã
   å¦æä½ æ¯å¨éè¡SQL客æ¶ç«¯æå çºå¾å°è¿åäºå¤ªå¤çè³æèåºç¾åé¡ï¼è«å¨éè¡å®¢æ¶ç
   «¯ä¹åå·è¡ä¸è¿°å½ä»¤ã
   
  4.14) æå¦ä½æè½ç¥éæéè¡çPostgreSQLççæ¬ï¼
  
   å¾ psql 裡ï¼è¼¸å¥ SELECT version();æ令ã
   
  4.15) æå¦ä½åµå»ºä¸åé è¨å¼æ¯ç¶åæéçæ¬ä½ï¼
  
   ä½¿ç¨ CURRENT_TIMESTAMPï¼
   CREATE TABLE test (x int, modtime TIMESTAMP DEFAULT CURRENT_TIMESTAMP );

  4.16) ææ樣é²è¡ outer join ï¼å¤é£æ¥ï¼ï¼
  
   PostgreSQL æ¡ç¨æ¨æºç SQL èªæ³æ¯æå¤é£æ¥ãé裡æ¯å©åä¾åï¼
   SELECT *
   FROM t1 LEFT OUTER JOIN t2 ON (t1.col = t2.col);

   ææ¯
   SELECT *
   FROM t1 LEFT OUTER JOIN t2 USING (col);

   éå©åçå¹çæ¥è©¢å¨ t1.col å t2.col ä¸åé£æ¥ï¼ä¸¦ä¸è¿å t1 中
   æææªé£æ¥çè¡ï¼é£äºå¨ t2 ä¸æ²æå¹éçè¡ï¼ã å³[å¤]é£æ¥ï¼RIGHT OUTER
   JOINï¼å°è¿å t2 ä¸æªé£æ¥çè¡ã å®å¨å¤é£æ¥ï¼FULL OUTER JOINï¼å°è¿å t1 å t2
   ä¸æªé£æ¥çè¡ã ééµå OUTER å¨å·¦[å¤]é£æ¥ãå³[å¤]é£æ¥åå®å¨[å¤]é£æ¥ä¸­
   æ¯å¯é¸çï¼æ®éé£æ¥è¢«ç¨±çºå§é£æ¥ï¼INNER JOINï¼ã
   
  4.17) å¦ä½ä½¿ç¨æ¶åå¤åè³æ庫çæ¥è©¢ï¼
  
   æ²æ辦æ³æ¥è©¢ç¶åè³æ庫ä¹å¤çè³æ庫ã
   å çºPostgreSQLè¦å è¼èè³æ庫ç¸éç系統ç®éï¼ç³»çµ±è¡¨ï¼ï¼å æ­
   ¤è·¨è³æ庫çæ¥è©¢å¦ä½å·è¡æ¯ä¸å®çã
   
   éå å¢å¼æ¨¡å¡ contrib/dblink
   å許æ¡ç¨å½æ¸èª¿ç¨å¯¦ç¾è·¨åº«æ¥è©¢ãç¶ç¶ç¨æ¶ä¹å¯ä»¥åæé£æ¥å°ä¸åçè³æ庫å·è
   ¡æ¥è©¢ç¶å¾å¨å®¢æ¶ç«¯åä½µçµæã
   
  4.18) å¦ä½è®å½æ¸è¿åå¤è¡æå¤åè³æï¼
  
   å¨å½æ¸ä¸è¿åè³æè¨ééçåè½æ¯å¾å®¹æ使ç¨çï¼è©³æåè¦ï¼
   http://techdocs.postgresql.org/guides/SetReturningFunctions
   
  4.19) çºä»éº¼æå¨ä½¿ç¨ PL/PgSQL å½æ¸ååè¨æ表æææ¶å°é¯èª¤è³è¨ãrelation with OID
  ##### does not existãï¼
  
   PL/PgSQL æç·©åå½æ¸çè³æ¬å§å®¹ï¼ç±æ¤å¸¶ä¾çä¸åä¸å¥½çå¯ä½ç¨æ¯è¥ä¸å
   PL/PgSQL
   å½æ¸è¨ªåäºä¸åè¨æ表ï¼ç¶å¾è©²è¡¨è¢«åªé¤ä¸¦é建äºï¼åå次調ç¨è©²å½æ¸å°å¤
   ±æï¼ å çºç·©åçå½æ¸å§å®¹ä»ç¶æåèçè¨æ表ã解決çæ¹æ³æ¯å¨ PL/PgSQL 中
   ç¨EXECUTE å°è¨æ表é²è¡è¨ªåãé樣æä¿èæ¥è©¢å¨å·è¡å總æ被éæ°è§£æã
   
  4.20) ç®åæåªäºè³æè¤å¯«(replication)æ¹æ¡å¯ç¨ï¼
  
   ãè¤å¯«ãåªæ¯ä¸åè¡èªï¼æ好幾種è¤å¯«æè¡å¯ç¨ï¼æ¯ç¨®é½æåªé»å缺é»ï¼
   
   主/å¾å¼è¤å¯«æ¹å¼æ¯å許ä¸å主伺æå¨æ¥åè®/寫çç³è«ï¼èå¤åå¾ä¼ºæå¨åªè½æ¥å
   è®/SELECTæ¥è©¢çç³è«ï¼ ç®åææµè¡ä¸åè²»ç主/å¾PostgreSQLè¤å¯«æ¹æ¡æ¯
   Slony-I ã
   
   å¤å主伺æå¨çè¤å¯«æ¹å¼å許å°è®/寫çç³è«ç¼é給å¤å°ç主æ©ï¼é種æ¹å¼ç±æ¼é
   è¦å¨å¤å°ä¼ºæå¨ä¹éåæ¥è³æè®å å¯è½æ帶ä¾è¼å´éçæ§è½æ失ï¼Pgcluster
   æ¯ç®åé種æ¹æ¡ä¸æ好çï¼ä¸¦ä¸éå¯ä»¥åè²»ä¸è¼ã
   
   ä¹æä¸äºåæ¥éä»è²»ååºæ¼ç¡¬é«çè³æè¤å¯«æ¹æ¡ï¼æ¯æä¸è¿°å種è¤å¯«æ¨¡åã
   
  4.21) çºä½æ¥è©¢çµæ顯示ç表åææ¬åèæçæ¥è©¢èªå¥ä¸çä¸åï¼çºä½å¤§å¯«çæä¸è½ä¿çï¼
  
   æ常è¦çåå æ¯å¨åµå»ºè¡¨æå°è¡¨åææ¯æ¬å使ç¨äºéå¼è( ' '
   )ï¼ç¶ä½¿ç¨äºéå¼èå¾ï¼è¡¨åææ¬åï¼ç¨±çºæ¨è符ï¼åå²ææ¯åå 大å°å¯«çï¼
   éæè¬èä½ å¨æ¥è©¢æ表åææ¬åä¹æ使ç¨éå¼èï¼ä¸äºå·¥å·è»é«ï¼å pgAdmin
   æå¨ç¼åºåµå»ºè¡¨çæ令æèªåå°å¨æ¯åæ¨è符ä¸å éå¼èã å æ¤ï¼çºäºæ¨è­
   符ççµ±ä¸ï¼ä½ æ該ï¼
     * å¨åµå»ºè¡¨æé¿åå°æ¨è符使ç¨éå¼èå¼èµ·ä¾ã
     * å¨æ¨è符ä¸åªä½¿ç¨å°å¯«åæ¯ã
     * ï¼çºäºèå·²åå¨çæ¨è符ç¸åï¼å¨æ¥è©¢ä¸ä½¿ç¨éå¼èå°æ¨è符å¼èµ·ä¾ã