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about joins

about joins# Database - 数据库

s*i2003-02-28 08:02

1 楼

I read that a temp table is always created for
joins, with number of rows equals to the multiple
of all tables. is this true? sounds terrible if
I join two or more tables if the rows are not small...

c*r2003-02-28 08:02

2 楼

It is not true.

【在 s**********i 的大作中提到】

: I read that a temp table is always created for
: joins, with number of rows equals to the multiple
: of all tables. is this true? sounds terrible if
: I join two or more tables if the rows are not small...

xt2003-02-28 08:02

3 楼

It is wrong. That is the mathematical expression of joins,
but it has nothing to do with the real time joins.

n*m2003-02-28 08:02

4 楼

But as know, it temp storage(we call it workfile) did been generated in
non-top level join. Certainly, it is not the representation of the
mathematical expression. Instead, it ususally only contains column/rows
that requried.

【在 xt 的大作中提到】

: It is wrong. That is the mathematical expression of joins,
: but it has nothing to do with the real time joins.