Question

I’ve just solved an interesting problem using MySQL’s IN, but I don’t know what this “trick” is called.

In my design I needed to filter out rows that either did not require a certain skill, or for which the skill name and the skill level were met. Here’s the solution:

SELECT * FROM table WHERE
    skillname = "" OR
    (skillname, skilllevel) IN (
        SELECT name, level FROM skills WHERE user="Mikhail"
    )

I didn’t know that expr IN (value,…), as according to dev.mysql.com both expr and value can be multiple columns.

What is this called, and are there more shortcuts like these?
More importantly – is there a way to convert this query to match skilllevel as “greater than or equal to”?

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Solution as per @yokoloko (though he won’t admit it)

SELECT * FROM t1 WHERE
    skillname = "" OR
    skillname IN (
        SELECT name FROM skills WHERE user="Mikhail" AND level >= t1.skilllevel
    )

Answer 1

i don’t know how is it called but if I understand well you can do something like this to get the greater than :

SELECT * FROM table t1 WHERE
    skillname = "" OR
    (skillname, skilllevel) IN (
        SELECT name, level FROM skills s WHERE user="Mikhail" and t1.skilllevel >= s.level
    )

But I don’t know if it’s really well optimized.