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oracle distinct

oracle distinct
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distinctÕâ¸ö¹Ø¼ü×ÖÀ´¹ýÂ˵ô¶àÓàµÄÖØ¸´¼Ç¼ֻ±£ÁôÒ»Ìõ£¬µ«ÍùÍùÖ»Óà ËüÀ´·µ»Ø²»Öظ´¼Ç¼µÄÌõÊý£¬¶ø²»ÊÇÓÃËüÀ´·µ»Ø²»ÖؼǼµÄËùÓÐÖµ¡£ÆäÔ­ÒòÊÇdistinctÖ»ÓÐÓöþÖØÑ­»·²éѯÀ´½â¾ö£¬¶øÕâÑù¶ÔÓÚÒ»¸öÊý¾ÝÁ¿·Ç³£´óµÄÕ¾À´Ëµ£¬ÎÞÒÉÊÇ»áÖ±½ÓÓ°Ï쵽ЧÂʵġ£
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   id        name
   1           a
   2           b
   3           c
   4           c
   5           b
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select distinct name from table
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name
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   b
   c
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select distinct name, id from table
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---------- 
id name
   1 a
   2 b
   3 c
   4 c
   5 b
distinctÔõôûÆð×÷Óã¿×÷ÓÃÊÇÆðÁ˵쬲»¹ýËûͬʱ×÷ÓÃÁËÁ½¸ö×ֶΣ¬Ò²¾ÍÊDZØÐëµÃidÓëname¶¼ÏàͬµÄ²Å»á±»Åųý¡£¡£¡£¡£¡£¡£¡£
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select id, distinct name from table
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select *, count(distinct name) from table group by name
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   id name count(distinct name)
   1 a 1
   2 b 1
   3 c 1
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Oracle wait problems and potential solutions

Wait Problem Potential Fix Sequential Read Indicates many index reads—tune the code (especially joins) Scattered Read Indicates many full table scans—tune the code; cache small tables ......

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oracle¿Í»§¶Ë Á¬½ÓPL/SQL

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D:\oracle\product\10.2.0\db_1\NETWORK\ADMIN\tnsnames.ora
# tnsnames.ora Network Configuration File: D:\oracle\product\10.2.0\db_1\network\admin\tnsnames.ora
# Generated by Oracle configuration tools.
SQLCLUB =
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