How to set a constraint on non-unique fields?

Hi list, I hope this is not OT here, but I'm no SQL guru and sure some
know this. I have two tables:

(just in short format)
multilang (id int, language int, text text);
types (id int, textid references multilang(id) on delete restrict);

But that doesn't work out, because "id" in multilang is not unique. For
one "id", there can be several "language" values, having a text in that
language. Now in table types, I want to make sure that "textid" MUST
exist in multilang, and cannot be deleted when having references. How
would I do that?

mfg zmi
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