没A没B / 说A就A: no A, no B; no sooner said than done
【五19】【五20】四字格 / set structures
Tone colorsā tone 1á tone 2ǎ tone 3à tone 4a neutral
没A没B means "without A or B": both halves of a pair are missing, which often sounds like a reproach or a hardship (没大没小: no respect for age or rank; 没日没夜: day and night without a break; 没吃没喝: nothing to eat or drink). 说A就A means "no sooner said than done": you act the moment you mention it, without hesitating.
In 说A就A the same one-syllable verb is repeated: 说走就走, 说干就干, 说买就买, 说来就来. Before a noun you add 的: 说走就走的旅行 is the spur-of-the-moment trip. Both belong to the 四字格 family, like 不A不B and 有A有B (HSK 6), but 没A没B describes a lack and 说A就A an immediate decision.
Register: spoken or lively prose, never solemn. Most 没A没B expressions are fixed by usage (A and B make a pair of opposites or complements), so you can't coin them freely. For a plain negation, 没有A也没有B is more neutral.
Examples
他说走就走，第二天就出发了。
Tā shuō zǒu jiù zǒu, dìèr tiān jiù chūfā le.No sooner said than done: he set off the very next day.
大家说干就干，一个下午就把房间收拾好了。
Dàjiā shuō gàn jiù gàn, yí ge xiàwǔ jiù bǎ fángjiān shōushi hǎo le.Everyone got to work at once, and the room was tidy within an afternoon.
我们想来一次说走就走的旅行，可是没有时间。
Wǒmen xiǎng lái yí cì shuō zǒu jiù zǒu de lǚxíng, kěshì méiyǒu shíjiān.We'd love a spur-of-the-moment trip, but we have no time.
你这孩子，怎么没大没小的，直接叫老师的名字？
Nǐ zhè háizi, zěnme méi dà méi xiǎo de, zhíjiē jiào lǎoshī de míngzi?Where are your manners, calling the teacher by name?
为了准备考试，他没日没夜地复习了一个星期。
Wèile zhǔnbèi kǎoshì, tā méi rì méi yè de fùxí le yí ge xīngqī.To prepare for the exam, he revised day and night for a whole week.
那年家里没吃没喝，全靠邻居帮忙才过了年。
Nà nián jiā lǐ méi chī méi hē, quán kào línjū bāngmáng cái guò le nián.That year the family had nothing to eat or drink, and only the neighbours' help got them through the New Year.
Common mistakes
✗ 说走就去 → ✓ 说走就走 (the same verb is repeated).
✗ 没有大没有小 → ✓ 没大没小 (one 没 each, no 有).
✗ 说走就走旅行 → ✓ 说走就走的旅行 (before a noun, 的 is needed).