mysql structure double unique

I am trying to make a mysql table and have got stuck with making it.

2 columns required:

aid
bid

The trick is aid is not unique and bid is not unique, but the combination of aid-bid IS unique.

EG:

a b ok?
0 1 y
0 2 y
0 7 y
1 1 y
1 7 y
8 3 y
0 7开发者_StackOverflow中文版 N - since 0 7 is already in table...

How can I make this table in sql so it works?

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create table my_table (
a int,
b int,
unique key (a,b) );

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You need to create a unique index for those columns:

CREATE UNIQUE INDEX id_index ON mytable (aid,bid);

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Just add a unique constraint to the table

ALTER TABLE t ADD UNIQUE KEY (aid, bid);

Then change your code to trap the exception when you try to insert a duplicate key.