| 语法 | LIMIT [offset,] n BY expr1 [, expr2 ...] |
|---|---|
| 语义 | 分组内按当前 ORDER BY 的顺序取前 n 行 |
| 叠加 | 末尾可再写普通 LIMIT 限制总返回行数 |
示例
示例
-- 每个 region 取最近 3 条记录
SELECT region, ts, value
FROM metrics
ORDER BY ts DESC
LIMIT 3 BY region;
-- 总共只返回 20 行
SELECT region, ts, value
FROM metrics
ORDER BY ts DESC
LIMIT 3 BY region
LIMIT 20;LIMIT BY 的分组结果不保证按组输出，外层再 ORDER BY 才有稳定展示顺序。