When to use subjunctive with "no sé"

Question

I've seen the subjunctive used with "no sé" before but I can't remember how to know when to use it or not. I know that "No sé si lo volveremos a ver" doesn't use it but when do you actually use it? Thanks.

any example? No se de que hablas, la verdad. - juanmelgar, Mar 17, 2014

¿Son correctos en cualquiera circunstancia los siguientes?-- - SlimNm, Mar 18, 2014

No sé lo que está pasando //// No sé lo que esté pasando - SlimNm, Mar 18, 2014

No entiendo que pasa. - annierats, Mar 18, 2014

Answer 1

Bosque has it half way

There are people who would say.

no sé que hicieramos si no estuvieras aquí.

The normal way to say and I am not sure if it is the only correct way would be:

No sé que haríamos si no estuvieras aquí

I don't know what would we do if you weren't here.

edit to answer slim nm comment:

the first one means exactly what I said in English. It can be applied in the past tense too.

What I don't know is if it is grammatically sound way to say it (the first one in Spanish) but people use it like I outlined it in English.

I'm pretty sure the first example is not correct, since it doesn't mean the same thing as the 2nd one (and probably doesn't even make grammatical sense). - SlimNm, Mar 18, 2014

They both make sense. - annierats, Mar 18, 2014

Thanks chileno. - ray76, Mar 18, 2014

What does "no sé que hicieramos si no estuvieras aqui" even mean? Is the closest translation "I don't know what we were to have done if you hadn't been there?" I think using "would" in the first part woudl make more sense... - SlimNm, Mar 18, 2014

Correct, but there are people who say stuff like that. - chileno, Mar 19, 2014

Answer 2

This is not something I know for sure, but the only time it makes sense to me is if you follow it with “que” meaning “that” and put a sentence that you disbelieve. But I would always use creer there myself and so have never used this construction.

Not “qué” or “lo que” to translate as what, and almost never “si”- although I think you can say “no sé si sea” in some places (and maybe not others).

So “I don’t know that he did it” (and I don’t think he did): No sé que lo hiciera- no creo que lo hiciera.

But not “I don’t know what he did”- No sé qué hizo- no se lo que hizo.

Also not “ I don’t know if he did it” – No sé si lo hizo.

Please do not take this as something I know for sure, I am putting down my thought for discussion and for myself to learn from the analysis and they should only be considered correct if a native speaker confirms them.

Answer 3