〜さえ〜ば
As long as, if only… (that's enough)machine translation
FormationNoun + さえ + ば-form; verb ます-form (minus ます) + さえすれば; て-form + さえいれば
〜さえ〜ば states the MINIMUM, sole condition: as long as A is satisfied, outcome B is guaranteed to be fine, and nothing else matters. これさえあれば大丈夫 (as long as I have this, I'm fine).
Connection: with nouns, place さえ right after the noun and put the following clause in the ば-form: 天気さえよければ (as long as the weather is good). With verbs, take the ます-form minus ます and add さえすれば: 飲みさえすれば (as long as you drink it…); for ongoing states, use the て-form + さえいれば: 生きてさえいれば (as long as you're alive).
Compared with だけ, the difference lies in the structure: だけ only says "only, solely," while さえ〜ば is a complete conditional package meaning "as long as… that's enough." Also don't confuse it with さえ on its own meaning "even" — that is a separate emphasis pattern, with no ば-form following.
Examples
この薬を飲みさえすれば、すぐよくなりますよ。
As long as you take this medicine, you'll get better right away.
天気さえよければ、明日は山に登るつもりです。
As long as the weather is good, I plan to climb the mountain tomorrow.
あなたさえそばにいてくれれば、ほかには何もいりません。
As long as you're by my side, I don't need anything else.