Unique index not based on words order?

Is it possibile to have a开发者_Go百科 mysql UNIQUE index on a varchar field not based on the words order?

I mean if there is a row with key1 key2, and I try to insert key2 key1 mysql should throw an error.

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You could achieve this effect by adding before insert and before update triggers to the table; they could check whether a row with the fields reversed exists or not before inserting/updating if it doesn't, or forcing an error if it does.

See here for more information.

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If you set the indexed to UNIQUE, you will not be able to enter the identical data twice - numbers, words or otherwise.

If you wish to achieve something otherwise, you'll have to set a new non-unique field in your database then you'll be able achieve it using external code and queries (PHP, C#).

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Create a trigger to do this.

i.e.

CREATE TRIGGER trigger_name BEFORE INSERT ON table_name
FOR EACH ROW
BEGIN
   IF ((SELECT COUNT(*) FROM table WHERE col2=NEW.col1 OR col1=NEW.col2) <> 0)
   THEN
     CALL this_procedure_does_not_exist();
   END IF
END