sqlite计数不同的事件

Question

编写一个sqlite查询的最佳方法是在选择不同的colA＆＃39之后计算colC的出现次数？

SELECT colA, colB, colC FROM myTable WHERE colA IN ('121', '122','123','124','125','126','127','128','129');

注意ColA需要与众不同。

虽然很接近，但这些结果不正确。

它应该返回：
123一只猫1 124 b狗1 125 e蛇2
126 f鱼1 127克蛇2

Answer 1

您可以按colA汇总以获得您想要的大部分内容：

select colA, count(*)
from myTable
where colA in ('121', '122','123','124','125','126','127','128','129')
group by colA;

目前还不清楚您是如何获得colB和colC的。以下适用于您的示例数据：

select colA, min(colB), max(colC), count(*)
from myTable
where colA in ('121', '122','123','124','125','126','127','128','129')
group by colA;

Answer 2

WITH t AS (
  SELECT colA, min(colB) AS colB, max(colC) AS colC
    FROM myTable
    WHERE colA IN ('121', '122','123','124','125','126','127','128','129')
    GROUP BY colA
)
SELECT t.*, c.colC_count
  FROM t
  JOIN (
    SELECT colC, count(*) AS colC_count
      FROM t
      GROUP BY colC
  ) c ON c.colC = t.colC

说明：

第一个子查询（在WITH内）获得所需的结果，但没有计数列。第二个子查询（在JOIN内）计算所需结果中的每个colC值重复，并将此计数返回到最终结果。

由于第一个子查询在两个地方使用，因此非常有用的WITH子句。更多信息：https://www.sqlite.org/lang_with.html

---

在版本3.8.3之前查询SQLite：

SELECT t.*, c.colC_count
  FROM (
    SELECT colA, min(colB) AS colB, max(colC) AS colC
      FROM myTable
      WHERE colA IN ('121', '122','123','124','125','126','127','128','129')
      GROUP BY colA
    ) t
  JOIN (
    SELECT colC, count(*) AS colC_count
      FROM (
        SELECT max(colC) AS colC
          FROM myTable
          WHERE colA IN ('121', '122','123','124','125','126','127','128','129')
          GROUP BY colA
        ) c
      GROUP BY colC
  ) c ON c.colC = t.colC

Answer 3

我认为您正在寻找COUNT(colC) + GROUP BY (colA)的组合。像这样：

SELECT colA, colB, colC, COUNT(colC)
FROM myTable
WHERE colA IN ('121', '122','123','124','125','126','127','128','129')
GROUP BY (colA);

另见this Q&A。