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1.select  * from A where a.a='a';
  Ö´ÐÐ˳Ðò ÏÈÖ´ÐÐ from ÔÚÖ´ÐÐ where ÖеĶ«Î÷ £¬×îºóÖ´ÐÐ select
2.ÁÐÖµÁ¬½Ó db2 oracle ||  , mysql concat(column1,'sss',column2) sqlServlerʹÓÃ+Á¬½Ó;
3. case when  ±í´ïʽ then ''
            when  ±í´ïʽ then ''
             else    ''
   end
4. ÏÞÖÆ·µ»ØµÄÐÐÊý
 ÔÚoracleÖÐʹÓÃrownum <= n ÏÞÖÆÐÐÊý
 ÔÚdb2ÖÐʹÓÃfetch first 5 rows only
 ×¢Òâ oracleÖÐÈç¹ûʹÓÃrownum =5 Êǵò»µ½µÚÎåÐеģ¬ÒòΪoracleµÄ²éѯԭÀí»ñȡһÐк󸳸øÐкţ¬Èç¹ûÐкÅÂú×ãÌõ¼þ·µ»Ø·ñÔòÉáÆú£¬ÕâÑùÓÀÔ¶µÃ²»µ½µÚÎåÐУ¬ÓÀÔ¶ÊǵÚÒ»ÐкŲ¢½ÓÉáÆú£¬ËùÒÔÒªÏëµÃµ½µÚÎåÐУ¬±ØÐëµÃµ½Ç°ËÄÐУ¬ËùÒÔ²éѯǰÎåÐбØÐëÊÇ<= 5;
5.null ÒªÏëÅжÏÖµÊÇ·ñΪnull±ØÐëΪ is null  £¬ null²»ÄÜÓõÈÓÚ=ºÍ²»µÈÓÚ<> ºÍÈκÎÖµ±È½Ï°üÀ¨null
6¡£°´Ä£Ê½²éѯ like '%a' 


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Asp.NetÖÐsql server 2000/2005 Á¬½Ó×Ö·û´®


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SQL 2000:
static string StrConn = "server=.;uid=sa;pwd=sa;database=MyCUDS";
SQL2005:
con = new SqlConnection(@"Server=.\SQLExpress;Database=db_CMS;Persist Security Info=True;User ID=sa;Password=Masslong"); ......

sql having ºÍwhereµÄÇø±ð

  ×î½üÔÚѧϰoracleµÄʱºòÓöµ½Ò»¸öÎÊÌ⣬ÀÏÊÇŪ²»Çå³þwhere ºÍhavingµÄÇø±ð£¬ÔÚÍøÉϲéÒ»²é£¬¸Ð¾õ»¹¿ÉÒÔ£¬°ÑÒÔÏÂÎÒ²éµÄ×ÊÁÏÍÆ¼ö¸ø´ó¼Ò¡£
ÔÚselect Óï¾äÖпÉÒÔʹÓÃgroup by ×Ӿ佫Ðл®·Ö³É½ÏСµÄ×飬Ȼºó£¬Ê¹ÓþÛ×麯Êý·µ»ØÃ¿Ò»¸ö×éµÄ»ã×ÜÐÅÏ¢£¬ÁíÍ⣬¿ÉÒÔʹÓÃhaving×Ó¾äÏÞÖÆ·µ»ØµÄ½á¹û¼¯¡£group&n ......

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1. ¿ªÆôÒ»¸öÊÂÎñÖ´ÐвåÈëÊý¾ÝµÄ²Ù×÷¡£
BEGIN TRAN t
INSERT INTO Customer
SELECT 'a','a'
2. Ö´ÐÐÒ»Ìõ²éѯÓï¾ä¡£
SELECT * from Customer WITH (NOLOCK)
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sqlµ÷ÓÅÖ® ѰÕÒÎÒÃÇ×î¸ÐÐËȤµÄÓï¾ä

Tuning an Application / Reducing Load
If your whole application is performing suboptimally, or if you are attempting to
reduce the overall CPU or I/O load on the database server, then identifying
resource-intensive SQL involves the following steps:
1. Determine which period in the day you would ......
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