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<p>¸üÐÂÏÂÎÊÌâ： <br>±í：TBL_Info <br>×Ö¶Î： <br>    infoId int <br>    title  varchar(20) <br>    Content  text <br>    byUser  varchar(20) <br>    createTime datetime <br><br>1¡¢ÈçºÎɾ³ý±íÖÐÊý¾ÝÏàͬµÄÊý¾ÝÄØ？（Ö÷¼ü³ýÍâ） <br>2¡¢ÈçºÎɾ³ýÊý¾Ý±íÖÐij¸ö×Ö¶ÎÊý¾ÝÏàͬµÄÊý¾ÝÄØ(±ÈÈçtitle：ɾ³ýËùÓÐtitleÏàͬµÄÊý¾Ý)？ <br>3¡¢ÈçºÎͳ¼Æ±íÖÐtitleÏàͬÊý¾ÝµÄÊýÄ¿？</p>
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<p><span style="color: #008080;">--</span><span style="color: #008080;">1</span><span style="color: #008080;"> --</span><span style="color: #008080;">1.1Ïàͬʱ±£Áô×îСµÄinfoId</span><span style="color: #008080;"><br></span><span style="color: #0000ff;">delete</span><span style="color: #000000;"> TBL_Info </span><span style="color: #0000ff;">from</span><span style="color: #000000;"> TBL_Info t </span><span style="color: #0000ff;">where</span><span style="color: #000000;"> infoId </span><span style="color: #808080;">not</span><span style="color: #000000;"> </span><span style="color: #808080;">in</span><span style="color: #000000;"> (</span><span style="color: #0000ff;">select</span><span style="color: #000000;"> </span><span style="color: #ff00ff;">min</span><span style="color: #000000;">(id) </span><span style="color: #0000ff;">from</span><span style="color: #000000;"> infoId </span><span style="color: #0000ff;">where</span><span style="color: #000000;"> title </span><span style="color: #808080;">&#61;</span><span style="color: #000000;"> t.title </span><span style="color: #808080;">and</span><span style="color: #000000;"> Content </span><span style="color: #808080;">&#61;</span><span style="color: #000000;"> t.Content </span><span style="color: #808080;">and</span><span style="color: #000000;"> byUser </span><span style="color: #808080;">&#61;</span><span style="color: #000000;"> t.byUser </span><span style="color: #808080;">and</span><span style="color: #000000;"> createTime </span><span style="color: #808080;">&#61;</span><span style="color: #000000;"> t.createTime)<br></span><span style="color: #008080;">--</span><span style="color: #008080;">1.1Ïàͬʱ±£Áô×î´óµÄinfoId</span><span style="color: #008080;"><br></span><span style="color: #0000ff;">delete</span><span style="color: #000000;"> TBL_Info </span><span style="color: #0000ff;">from</span><span style="color: #000000;"> TBL_Info t </span><span style="color: #0000ff;">where</span><span style="color: #000000;"> infoId </span><span style="color: #808080;">not</span><span style="color: #000000;"> </span><span style="color: #808080;">in</span><span style="color: #000000;"> (</span><span style="color: #0000ff;">select</span><span style="color: #000000;"> </span><span style="color: #ff00ff;">max</span><span style="color: #000000;">(id) </span><span style="color: #0000ff;">from</span><span style="color: #000000;"> infoId </span><span style="color: #0000ff;">where</span><span style="color: #000000;"> title </span><span style="color: #808080;">&#61;</span><span style="color: #000000;"> t.title </span><span style="color: #808080;">and</span><span style="color: #000000;"> Content </span><span style="color: #808080;">&#61;</span><span style="color: #000000;"> t.Content </span><span style="color: #808080;">and</span><span style="color: #000000;"> byUser </span><span style="color: #808080;">&#61;</span><span style="color: #000000;"> t.byUser </span><span style="color: #808080;">and</span><span style="color: #000000;"> createTime </span><span style="color: #808080;">&#61;</span><span style="color: #000000;"> t.createTime)<br><br></span><span style="color: #008080;">--</span><span style="color: #008080;">2</span><span style="color: #008080;"><br></span><span style="color: #0000ff;">delete</span><span style="color: #000000;"> </span><span style="color: #0000ff;">from</span><span style="color: #000000;"> TBL_Info </span><span style="color: #0000ff;">where</span><span style="color: #000000;"> title </span><span style="color: #808080;">in</span><span style="color: #000000;"> (</span><span style="color: #0000ff;">select</span><span style="color: #000000;"> title </span><span style="color: #0000ff;">from</span><span style="color: #000000;"> TBL_Info </span><span style="color: #0000ff;">group</span><span style="color: #000000;"> </span><span style="color: #0000ff;">by</span><span style="color: #000000;"> title </span><span style="color: #0000ff;">having</span><span style="color: #000000;"> </span><span style="color: #ff00ff;">count</span><span style="color: #000000;">(</span><span style="font-weight: bold; color: #800000;">1</span><span style="color: #000000;">) </span><span style="color: #808080;">&gt;</span><span style="color: #000000;"> </span><span style="font-weight: bold; color: #800000;">1</span><span style="color: #000000;">)<br><br></span><span style="color: #008080;">--</span><span style="color: #008080;">3</span><span style="color: #008080;"><br></span><span style="color: #0000ff;">select</span><span style="color: #000000;"> title , </span><span style="color: #ff00ff;">count</span><span style="color: #000000;">(</span><span style="font-weight: bold; color: #800000;">1</span><span style="color: #000000;">) </span><span style="color: #0000ff;">from</span><span style="color: #000000;"> TBL_Info </span><span style="color: #0000ff;">group</span><span style="color: #000000;"> </span><span style="color: #0000ff;">by</span><span style="color: #000000;"> title<br></span><span style="color: #0000ff;"