mysql - SQL限制组数

Question

我正在尝试创建一个简单的分页，但它似乎无法限制结果的数量。

SELECT * FROM visits GROUP by clientID ORDER BY 'date' LIMIT $from, $to

我只想获得每个客户的第一次访问(按时间顺序)并对结果进行分页。

如果我使用 $from = 6, $to = 12 进行查询，它会返回 8 行而不是 7 行。

我做错了什么？

Answer 1

来自 LIMIT 上的 MySQL 文档子句

The LIMIT clause can be used to constrain the number of rows returned by the SELECT statement. LIMIT takes one or two numeric arguments, which must both be nonnegative integer constants (except when using prepared statements).

With two arguments, the first argument specifies the offset of the first row to return, and the second specifies the maximum number of rows to return. The offset of the initial row is 0 (not 1).

当你选择$from为6，$to为12；您不是从 6 到 12 中选择；您将选择 12 行，从 $from + 1 = 7 开始。