向高手请教

zhongzengx

如何将一下的数据中daima不同的数据，提取前20个数据；先谢谢了
daima riqi
000001 2009-6-12
000001 2009-6-11
000001 2009-6-10
000001 2009-6-9
000001 2009-6-8
000001 2009-6-5
000001 2009-6-4
000001 2009-6-3
000001 2009-6-2
000001 2009-6-1
000001 2009-5-27
000001 2009-5-26
000001 2009-5-25
000001 2009-5-22
000001 2009-5-21
000001 2009-5-20
000001 2009-5-19
000001 2009-5-18
000001 2009-5-15
000001 2009-5-14
000001 2009-5-13
000001 2009-5-12
000001 2009-5-11
000002 2009-6-12
000002 2009-6-11
000002 2009-6-10
000002 2009-6-9
000002 2009-6-8
000002 2009-6-5
000002 2009-6-4
000002 2009-6-3
000002 2009-6-2
000002 2009-6-1
000002 2009-5-27
000002 2009-5-26
000002 2009-5-25
000002 2009-5-22
000002 2009-5-21
000002 2009-5-20
000002 2009-5-19
000002 2009-5-18
000002 2009-5-15
000002 2009-5-14
000002 2009-5-13
000002 2009-5-12
000002 2009-5-11
000004 2009-6-12
000004 2009-6-11
000004 2009-6-10
000004 2009-6-9
000004 2009-6-8
000004 2009-6-5
000004 2009-6-4
000004 2009-6-3
000004 2009-6-2
000004 2009-6-1
000004 2009-5-27
000004 2009-5-26
000004 2009-5-25
000004 2009-5-22
000004 2009-5-21
000004 2009-5-20
000004 2009-5-19
000004 2009-5-18
000004 2009-5-15
000004 2009-5-14
000004 2009-5-13
000004 2009-5-12
000004 2009-5-11
000005 2009-6-12
000005 2009-6-11
000005 2009-6-10
000005 2009-6-9
000005 2009-6-8
000005 2009-6-5
000005 2009-6-4
000005 2009-6-3
000005 2009-6-2
000005 2009-6-1
000005 2009-5-27
000005 2009-5-26
000005 2009-5-25
000005 2009-5-22
000005 2009-5-21
000005 2009-5-20
000005 2009-5-19
000005 2009-5-18
000005 2009-5-15
000005 2009-5-14
000005 2009-5-13
000005 2009-5-12
000005 2009-5-11
000006 2009-6-12
000006 2009-6-11
000006 2009-6-10
000006 2009-6-9
000006 2009-6-8
000006 2009-6-5
000006 2009-6-4
000006 2009-6-3
000006 2009-6-2
000006 2009-6-1
000006 2009-5-27
000006 2009-5-26
000006 2009-5-25
000006 2009-5-22
000006 2009-5-21
000006 2009-5-20
000006 2009-5-19
000006 2009-5-18
000006 2009-5-15
000006 2009-5-14
000006 2009-5-13
000006 2009-5-12
000006 2009-5-11
000007 2009-6-12
000007 2009-6-11
000007 2009-6-10
000007 2009-6-9
000007 2009-6-8
000007 2009-6-5
000007 2009-6-4
000007 2009-6-3
000007 2009-6-2
000007 2009-6-1
000007 2009-5-27
000007 2009-5-26
000007 2009-5-25
000007 2009-5-22
000007 2009-5-21
000007 2009-5-20
000007 2009-5-19
000007 2009-5-18
000007 2009-5-15
000007 2009-5-14
000007 2009-5-13
000007 2009-5-12
000007 2009-5-11
000008 2009-6-12
000008 2009-6-11
000008 2009-6-10
000008 2009-6-9
000008 2009-6-8
000008 2009-6-5
000008 2009-6-4
000008 2009-6-3
000008 2009-6-2
000008 2009-6-1
000008 2009-5-27
000008 2009-5-26
000008 2009-5-25
000008 2009-5-22
000008 2009-5-21
000008 2009-5-20
000008 2009-5-19
000008 2009-5-18
000008 2009-5-15
000008 2009-5-14
000008 2009-5-13
000008 2009-5-12
000008 2009-5-11
000009 2009-6-12
000009 2009-6-11
000009 2009-6-10
000009 2009-6-9
000009 2009-6-8
000009 2009-6-5
000009 2009-6-4
000009 2009-6-3
000009 2009-6-2
000009 2009-6-1
000009 2009-5-27
000009 2009-5-26
000009 2009-5-25
000009 2009-5-22
000009 2009-5-21
000009 2009-5-20
000009 2009-5-19
000009 2009-5-18
000009 2009-5-15
000009 2009-5-14
000009 2009-5-13
000009 2009-5-12
000009 2009-5-11
000010 2009-6-12
000010 2009-6-11
000010 2009-6-10
000010 2009-6-9
000010 2009-6-8
000010 2009-6-5
000010 2009-6-4
000010 2009-6-3
000010 2009-6-2
000010 2009-6-1
000010 2009-5-27
000010 2009-5-26
000010 2009-5-25
000010 2009-5-22
000010 2009-5-21
000010 2009-5-20
000010 2009-5-19
000010 2009-5-18
000010 2009-5-15
000010 2009-5-14
000010 2009-5-13
000010 2009-5-12
000010 2009-5-11
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000011 2009-6-10
000011 2009-6-9
000011 2009-6-8
000011 2009-6-5
000011 2009-6-4
000011 2009-6-3
000011 2009-6-2
000011 2009-6-1
000011 2009-5-27
000011 2009-5-26
000011 2009-5-25
000011 2009-5-22
000011 2009-5-21
000011 2009-5-20
000011 2009-5-19
000011 2009-5-18
000011 2009-5-15
000011 2009-5-14
000011 2009-5-13
000011 2009-5-12
000011 2009-5-11
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000012 2009-5-26
000012 2009-5-25
000012 2009-5-22
000012 2009-5-21
000012 2009-5-20
000012 2009-5-19
000012 2009-5-18
000012 2009-5-15
000012 2009-5-14
000012 2009-5-13
000012 2009-5-12
000012 2009-5-11
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000014 2009-5-26
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000014 2009-5-22
000014 2009-5-21
000014 2009-5-20
000014 2009-5-19
000014 2009-5-18
000014 2009-5-15
000014 2009-5-14
000014 2009-5-13
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000014 2009-5-11
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000016 2009-6-10
000016 2009-6-9
000016 2009-6-8
000016 2009-6-5
000016 2009-6-4
000016 2009-6-3
000016 2009-6-2
000016 2009-6-1
000016 2009-5-27
000016 2009-5-26
000016 2009-5-25
000016 2009-5-22
000016 2009-5-21
000016 2009-5-20
000016 2009-5-19
000016 2009-5-18
000016 2009-5-15
000016 2009-5-14
000016 2009-5-13
000016 2009-5-12
000016 2009-5-11
000017 2009-6-12
000017 2009-6-11
000017 2009-6-10
000017 2009-6-9
000017 2009-6-8
000017 2009-6-5
000017 2009-6-4
000017 2009-6-3
000017 2009-6-2
000017 2009-6-1
000017 2009-5-27
000017 2009-5-26
000017 2009-5-25
000017 2009-5-22
000017 2009-5-21
000017 2009-5-20
000017 2009-5-19
000017 2009-5-18
000017 2009-5-15
000017 2009-5-14
000017 2009-5-13
000017 2009-5-12
000017 2009-5-11
000018 2009-6-12
000018 2009-6-11
000018 2009-6-10
000018 2009-6-9
000018 2009-6-8
000018 2009-6-5
000018 2009-6-4
000018 2009-6-3
000018 2009-6-2
000018 2009-6-1
000018 2009-5-27
000018 2009-5-26
000018 2009-5-25
000018 2009-5-22
000018 2009-5-21
000018 2009-5-20
000018 2009-5-19
000018 2009-5-18
000018 2009-5-15
000018 2009-5-14
000018 2009-5-13
000018 2009-5-12
000018 2009-5-11
000019 2009-6-12
000019 2009-6-11
000019 2009-6-10
000019 2009-6-9
000019 2009-6-8
000019 2009-6-5
000019 2009-6-4
000019 2009-6-3
000019 2009-6-2
000019 2009-6-1
000019 2009-5-27
000019 2009-5-26
000019 2009-5-25
000019 2009-5-22
000019 2009-5-21
000019 2009-5-20
000019 2009-5-19
000019 2009-5-18
000019 2009-5-15
000019 2009-5-14
000019 2009-5-13
000019 2009-5-12
000019 2009-5-11
000020 2009-6-12
000020 2009-6-11
000020 2009-6-10
000020 2009-6-9
000020 2009-6-8
000020 2009-6-5
000020 2009-6-4
000020 2009-6-3
000020 2009-6-2
000020 2009-6-1
000020 2009-5-27
000020 2009-5-26
000020 2009-5-25
000020 2009-5-22
000020 2009-5-21
000020 2009-5-20
000020 2009-5-19
000020 2009-5-18
000020 2009-5-15
000020 2009-5-14
000020 2009-5-13
000020 2009-5-12
000020 2009-5-11

todaynew

select daima,first(riqi) from 表 GROUP BY  daima

zhongzengx

要每个daima的前20条！谢谢