Question

我想执行'select count'查询增量值（按5）

像这些SQL查询一样：

SELECT COUNT(*) FROM ages WHERE ages.year BETWEEN 1990 and 1995
SELECT COUNT(*) FROM ages WHERE ages.year BETWEEN 1995 and 2000
..so fort and so on..

如何使其成为有效的单一查询？

Answer 1

SELECT COUNT(*) AS `count`, (ages.year DIV 5) * 5 AS bottom, 
    (ages.year DIV 5 + 1) * 5 AS top
FROM ages
GROUP BY (ages.year DIV 5) * 5, (ages.year DIV 5 + 1) * 5

SQL Fiddle example

请注意，这假设您实际上不想要在边界上重复计算这些值。它不是100％与原始查询完全一样。如果你确实想要重复计算，请尝试：

SELECT SUM(`count`) AS `count`, bottom, top
FROM
(
    SELECT COUNT(*) AS `count`, (ages.year DIV 5) * 5 AS bottom, 
        (ages.year DIV 5 + 1) * 5 AS top
    FROM ages
    GROUP BY (ages.year DIV 5) * 5, (ages.year DIV 5 + 1) * 5
    UNION ALL
    SELECT 1 AS `count`, ages.year - 5 AS bottom, ages.year AS top
    FROM ages
    WHERE MOD(ages.year, 5) = 0
) inclusive
GROUP BY bottom, top

SQL Fiddle example

MySQL'count'，其中年份范围是递增的

1 个答案: