As far as (one) knows; used to indicate the limits of the speaker's knowledge.
私の知る限り、彼はこれまで嘘をついたことがない。
As far as I know, he has never lied.
知る限りでは、その店はもう閉店したはずだ。
As far as I know, that shop should be closed now.
知る限り、この問題に対する前例はない。
To the best of my knowledge, there is no precedent for this issue.
彼女は、知る限り最も有能な候補者だ。
She is, as far as I know, the most capable candidate.