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mysql maximum columns <=1000?
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mysql maximum columns <=1000?# Database - 数据库
l*b
1
Is there any way to create a table with more than 1000 columns?!!
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aw
2
WHY DO YOU NEED SUCH A TABLE?
难以想象。

【在 l**b 的大作中提到】
: Is there any way to create a table with more than 1000 columns?!!
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l*b
3
e.g., a 20000x2000 matrix, which is very common for data mining.

【在 aw 的大作中提到】
: WHY DO YOU NEED SUCH A TABLE?
: 难以想象。

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aw
4
恕俺无知,你SURE你的一个RECORD有1000个ATTRIBUTES?ORACLE也就是1000的LIMIT,稍
微具体点讲讲你的DESIGN?

【在 l**b 的大作中提到】
: e.g., a 20000x2000 matrix, which is very common for data mining.
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l*b
5
We know that the common web server log file is just a flat text file.
suppose we have 2000 web pages in a web site. If a row records all pages
visited by a certain user (he may visit some of 2000 pages), and if 20000
users have been identified, how to load such records (in text file it would be
a 20000x2000 matrix, cell value is how many seconds the user spent on the
page.) into database?



【在 aw 的大作中提到】
: 恕俺无知,你SURE你的一个RECORD有1000个ATTRIBUTES?ORACLE也就是1000的LIMIT,稍
: 微具体点讲讲你的DESIGN?

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s*e
6
table 1: web page (page_id, ...
table 2: user ( user_id, ...
table 3: access record ( user_id, page_id, access_time )

【在 l**b 的大作中提到】
: We know that the common web server log file is just a flat text file.
: suppose we have 2000 web pages in a web site. If a row records all pages
: visited by a certain user (he may visit some of 2000 pages), and if 20000
: users have been identified, how to load such records (in text file it would be
: a 20000x2000 matrix, cell value is how many seconds the user spent on the
: page.) into database?
:
: 稍

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aw
7
lieb,你该回去复习DATABASE基本概念了,没有冒犯的意思。

would be
恕俺无知,你SURE你的一个RECORD有1000个ATTRIBUTES?ORACLE也就是1000的LIMIT,

【在 s***e 的大作中提到】
: table 1: web page (page_id, ...
: table 2: user ( user_id, ...
: table 3: access record ( user_id, page_id, access_time )

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l*b
8
Thanks, shuke. you are definitely right from the database design perspective.
Then, for table 3 we would have 40,000,000(much fewer if the original matrix
is a sparse matrix.) rows while having only 3 columns.
The only concern is that for separating into more tables, more aggregation
code (join query) need to be written when geting data back to do some
matrix-oriented computation.
Not sure which way is faster, the database tables or a single 20000x2000
matrix-looking text file, in terms of gett

【在 s***e 的大作中提到】
: table 1: web page (page_id, ...
: table 2: user ( user_id, ...
: table 3: access record ( user_id, page_id, access_time )

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l*b
9
flush) good reminder, not using database for such a long time...
too much text mining...

20000
the

【在 aw 的大作中提到】
: lieb,你该回去复习DATABASE基本概念了,没有冒犯的意思。
:
: would be
: 恕俺无知,你SURE你的一个RECORD有1000个ATTRIBUTES?ORACLE也就是1000的LIMIT,

avatar
b*e
10
exactly.

【在 aw 的大作中提到】
: lieb,你该回去复习DATABASE基本概念了,没有冒犯的意思。
:
: would be
: 恕俺无知,你SURE你的一个RECORD有1000个ATTRIBUTES?ORACLE也就是1000的LIMIT,

avatar
s*e
11
If you import data into a database, you'd better stick on database for
further computation as much as possible. For example, creating indexes
on user_id or page_id in table 3 could improve your join query performance
a lot. If you can't utilize the advantage of database, just forget it.

【在 l**b 的大作中提到】
: Thanks, shuke. you are definitely right from the database design perspective.
: Then, for table 3 we would have 40,000,000(much fewer if the original matrix
: is a sparse matrix.) rows while having only 3 columns.
: The only concern is that for separating into more tables, more aggregation
: code (join query) need to be written when geting data back to do some
: matrix-oriented computation.
: Not sure which way is faster, the database tables or a single 20000x2000
: matrix-looking text file, in terms of gett

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