处理表重复记录(查询和删除)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 | if not object_id( 'Tempdb..#T' ) is null drop table #T Go Create table #T([ID] int ,[ Name ] nvarchar(1),[Memo] nvarchar(2)) Insert #T select 1,N 'A' ,N 'A1' union all select 2,N 'A' ,N 'A2' union all select 3,N 'A' ,N 'A3' union all select 4,N 'B' ,N 'B1' union all select 5,N 'B' ,N 'B2' Go --I、Name相同ID最小的记录(推荐用1,2,3),方法3在SQl05时,效率高于1、2 方法1: Select * from #T a where not exists( select 1 from #T where Name =a. Name and ID<a.ID) 方法2: select a.* from #T a join ( select min (ID)ID, Name from #T group by Name ) b on a. Name =b. Name and a.ID=b.ID 方法3: select * from #T a where ID=( select min (ID) from #T where Name =a. Name ) 方法4: select a.* from #T a join #T b on a. Name =b. Name and a.ID>=b.ID group by a.ID,a. Name ,a.Memo having count (1)=1 方法5: select * from #T a group by ID, Name ,Memo having ID=( select min (ID) from #T where Name =a. Name ) 方法6: select * from #T a where ( select count (1) from #T where Name =a. Name and ID<a.ID)=0 方法7: select * from #T a where ID=( select top 1 ID from #T where Name =a. name order by ID) 方法8: select * from #T a where ID!> all ( select ID from #T where Name =a. Name ) 方法9(注:ID为唯一时可用): select * from #T a where ID in ( select min (ID) from #T group by Name ) --SQL2005: 方法10: select ID, Name ,Memo from ( select *, min (ID)over(partition by Name ) as MinID from #T a)T where ID=MinID 方法11: select ID, Name ,Memo from ( select *,row_number()over(partition by Name order by ID) as MinID from #T a)T where MinID=1 生成结果: /* ID Name Memo ----------- ---- ---- 1 A A1 4 B B1 (2 行受影响) */ --II、Name相同ID最大的记录,与min相反: 方法1: Select * from #T a where not exists( select 1 from #T where Name =a. Name and ID>a.ID) 方法2: select a.* from #T a join ( select max (ID)ID, Name from #T group by Name ) b on a. Name =b. Name and a.ID=b.ID order by ID 方法3: select * from #T a where ID=( select max (ID) from #T where Name =a. Name ) order by ID 方法4: select a.* from #T a join #T b on a. Name =b. Name and a.ID<=b.ID group by a.ID,a. Name ,a.Memo having count (1)=1 方法5: select * from #T a group by ID, Name ,Memo having ID=( select max (ID) from #T where Name =a. Name ) 方法6: select * from #T a where ( select count (1) from #T where Name =a. Name and ID>a.ID)=0 方法7: select * from #T a where ID=( select top 1 ID from #T where Name =a. name order by ID desc ) 方法8: select * from #T a where ID!< all ( select ID from #T where Name =a. Name ) 方法9(注:ID为唯一时可用): select * from #T a where ID in ( select max (ID) from #T group by Name ) --SQL2005: 方法10: select ID, Name ,Memo from ( select *, max (ID)over(partition by Name ) as MinID from #T a)T where ID=MinID 方法11: select ID, Name ,Memo from ( select *,row_number()over(partition by Name order by ID desc ) as MinID from #T a)T where MinID=1 生成结果2: /* ID Name Memo ----------- ---- ---- 3 A A3 5 B B2 (2 行受影响) */ --2、删除重复记录有大小关系时,保留大或小其中一个记录 --> --> (Roy)生成測試數據 if not object_id( 'Tempdb..#T' ) is null drop table #T Go Create table #T([ID] int ,[ Name ] nvarchar(1),[Memo] nvarchar(2)) Insert #T select 1,N 'A' ,N 'A1' union all select 2,N 'A' ,N 'A2' union all select 3,N 'A' ,N 'A3' union all select 4,N 'B' ,N 'B1' union all select 5,N 'B' ,N 'B2' Go --I、Name相同ID最小的记录(推荐用1,2,3),保留最小一条 方法1: delete a from #T a where exists( select 1 from #T where Name =a. Name and ID<a.ID) 方法2: delete a from #T a left join ( select min (ID)ID, Name from #T group by Name ) b on a. Name =b. Name and a.ID=b.ID where b.Id is null 方法3: delete a from #T a where ID not in ( select min (ID) from #T where Name =a. Name ) 方法4(注:ID为唯一时可用): delete a from #T a where ID not in ( select min (ID) from #T group by Name ) 方法5: delete a from #T a where ( select count (1) from #T where Name =a. Name and ID<a.ID)>0 方法6: delete a from #T a where ID<>( select top 1 ID from #T where Name =a. name order by ID) 方法7: delete a from #T a where ID> any ( select ID from #T where Name =a. Name ) select * from #T 生成结果: /* ID Name Memo ----------- ---- ---- 1 A A1 4 B B1 (2 行受影响) */ --II、Name相同ID保留最大的一条记录: 方法1: delete a from #T a where exists( select 1 from #T where Name =a. Name and ID>a.ID) 方法2: delete a from #T a left join ( select max (ID)ID, Name from #T group by Name ) b on a. Name =b. Name and a.ID=b.ID where b.Id is null 方法3: delete a from #T a where ID not in ( select max (ID) from #T where Name =a. Name ) 方法4(注:ID为唯一时可用): delete a from #T a where ID not in ( select max (ID) from #T group by Name ) 方法5: delete a from #T a where ( select count (1) from #T where Name =a. Name and ID>a.ID)>0 方法6: delete a from #T a where ID<>( select top 1 ID from #T where Name =a. name order by ID desc ) 方法7: delete a from #T a where ID< any ( select ID from #T where Name =a. Name ) select * from #T /* ID Name Memo ----------- ---- ---- 3 A A3 5 B B2 (2 行受影响) */ --3、删除重复记录没有大小关系时,处理重复值 --> --> (Roy)生成測試數據 if not object_id( 'Tempdb..#T' ) is null drop table #T Go Create table #T([Num] int ,[ Name ] nvarchar(1)) Insert #T select 1,N 'A' union all select 1,N 'A' union all select 1,N 'A' union all select 2,N 'B' union all select 2,N 'B' Go 方法1: if object_id( 'Tempdb..#' ) is not null drop table # Select distinct * into # from #T --排除重复记录结果集生成临时表# truncate table #T --清空表 insert #T select * from # --把临时表#插入到表#T中 --查看结果 select * from #T /* Num Name ----------- ---- 1 A 2 B (2 行受影响) */ --重新执行测试数据后用方法2 方法2: alter table #T add ID int identity --新增标识列 go delete a from #T a where exists( select 1 from #T where Num=a.Num and Name =a. Name and ID>a.ID) --只保留一条记录 go alter table #T drop column ID --删除标识列 --查看结果 select * from #T /* Num Name ----------- ---- 1 A 2 B (2 行受影响) */ --重新执行测试数据后用方法3 方法3: declare Roy_Cursor cursor local for select count (1)-1,Num, Name from #T group by Num, Name having count (1)>1 declare @con int ,@Num int ,@ Name nvarchar(1) open Roy_Cursor fetch next from Roy_Cursor into @con,@Num,@ Name while @@Fetch_status=0 begin set rowcount @con; delete #T where Num=@Num and Name =@ Name set rowcount 0; fetch next from Roy_Cursor into @con,@Num,@ Name end close Roy_Cursor deallocate Roy_Cursor --查看结果 select * from #T /* Num Name ----------- ---- 1 A 2 B (2 行受影响) */ |
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