Found or sought: qui connaît, qui connaisse

In a relative clause the subjunctive is not triggered by a word: it is a choice, and it says whether the thing exists. Je connais quelqu'un qui sait l'allemand. - I know someone who knows German (they exist). Je cherche quelqu'un qui sache l'allemand. - I am looking for someone who knows German (if there is anyone).

The glosses: I have found a hotel that is quiet. I am looking for a hotel that is quiet. There is no hotel that is quiet. My hotel, which is quiet, is full.

The clause starts with an ordinary relative pronoun, qui or que; only the verb's mood moves. For the forms of sache, puisse and veuille, see the present subjunctive conjugation.

Found or sought

An indicative relative clause states a fact about something that exists. A subjunctive one states a requirement for something you are still looking for. The main verb is the giveaway: chercher, vouloir, avoir besoin de, je voudrais.

• Je cherche un appartement qui soit calme. - I am looking for a flat that is quiet.
• Je voudrais une maison qui ait un jardin. - I would like a house that has a garden.
• Nous avons besoin d'un employé qui sache conduire. - We need an employee who can drive.

Find the thing and the mood flips back, because now there is something to state a fact about:

• J'ai trouvé un appartement qui est calme. - I have found a flat that is quiet.
• J'ai un employé qui sait conduire. - I have an employee who can drive.

On a scale from it exists to it does not, the mood follows the certainty:

One sentence, two meanings

After je cherche, both moods are correct French. English says them the same way; French does not.

In everyday speech the indicative is common in both senses; the subjunctive is what spells the doubt out. Getting it wrong rarely sounds broken: it makes a claim you did not mean.

A definite article settles it. Le guide qui connaît la région est arrivé. - The guide who knows the area has arrived. Le has already picked the guide out, so the clause is a fact about him: indicative. (After le seul, le premier or a superlative the subjunctive comes back; see below.)