MYSQL query issue with UPDATE

Question

I have this query:

UPDATE people 
SET column1 = (
    SELECT if(r.rand BETWEEN 103 AND 109, 110, r.rand)
    FROM ( SELECT floor(8+rand()*113) rand ) r
)

However, it sets the SAME random number to every row. How can I change it in order to give a different value to every row?

stivlo · Accepted Answer · 2011-09-25 17:26:03Z

1

It seems the problem comes from the subquery, if you could simplify your assignment like the following:

UPDATE people 
SET column1 = floor(8+rand()*113)

It would work the way you expect: each row has assigned a different random number. However the subquery returns a single value that is assigned to all the rows.

I guess that if you can't simplify the logic to remove the scalar subquery, you may have to write a stored procedure or a short program to do what you want.

answered Sep 25, 2011 at 17:26

stivlo

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1 Comment

Adam Strudwick Over a year ago

OR just run your query followed by UPDATE people SET column1 = 110 WHERE column1 BETWEEN 103 AND 109?

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