s****a
发帖数: 6521 | 1 mysql
怎样用一个表更新另一个表，如果主键存在就略过，不存在就写入？
包子 | l******g
发帖数: 6771 | 2 能不能用subquery？
t1 destination
t2 source
insert into t1
from
(
select rows on t2 but not on t1
) | s****a
发帖数: 6521 | 3
如果两表结构并不完全相同，而是想用主键来判断呢
【在 l******g 的大作中提到】
: 能不能用subquery？
: t1 destination
: t2 source
: insert into t1
: from
: (
: select rows on t2 but not on t1
: )
| l******g
发帖数: 6771 | 4 1. 两表结构并不完全相同
well, we have to assume everything you need for insert could be found from
f2, right? otherwise, you are missing data source anyway.
if that's true, then you can get from f2 section in the subquery, right?
2. 想用主键来判断
that's what you do in the subquery? 主键is primary key(s), right?
for quick example:
insert into t1
select fields from f2 from
(
t2 outer join t1 by key
minus
t2 equal join t1 by key
)
In short, you need to think about mathematics matirx before detailed
implementation with specific database.
【在 s****a 的大作中提到】
:
: 如果两表结构并不完全相同，而是想用主键来判断呢
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