The French verb savoir ("to know") does not take the subjunctive. Very often used with que to introduce a dependent clause, savoir and savoir que are all about certainty. Thus, they do not fulfill the subjunctive's basic requirement of uncertainty and emotion.
The subjunctive mood is used to express actions or ideas that are subjective or otherwise uncertain: will/wanting, emotion, doubt, possibility, necessity, judgment.
The French subjunctive is nearly always found in dependent clauses introduced by que or qui, and the subjects of the dependent and main clauses are usually different.
Savoir means "to know" information and facts or "to know how" to do something. In the passé composé, savoir means "to learn" or "to find out," again with no subjunctive. (The verb is quite different from the French verb connaître, which means "to know" a person or "to be familiar with" a person or thing.")
Je sais où il est.
I know where he is.
Je sais conduire.
I know how to drive.
(The conjugated savoir is followed by an infinitive when the meaning is "to know how.")
Savoir que is the conjugated savoir plus a dependent clause beginning with que.
Je sais qu'il l'a fait.
I know he did it.
J'ai su qu'il l'a fait.
I found out that he did it.
Savoir que is not normally used in negative and interrogative statements; it's far more natural to use a si clause in such cases, which means, once again, that the subjunctive is not used:
Je ne sais pas si vous avez raison.
I don't know if you're right.
Sais-tu s'il a raison ?
Do you know if he's right?
Quiz: Subjunctive or indicative?