[英]MYSQL : select sum(value)
我有一个带有2个字段的表格,如下所示:
Day_col | Value_col
2013-06-06 1
2013-06-05 2
2013-06-04 3
2013-06-03 4
2013-06-02 5
而且我想创建一个sql(3天后的sum(Value_col)-如果有3天或更多的天将是总和,如果少于3天不求和),然后接收如下结果:
Day_col | total
2013-06-06 9 <- total after '2013-06-06' 3 days are 5,4,3 is 9
2013-06-05 12 <- total after '2013-06-05' 3 days are 4,3,2 is 12
2013-06-04 -- <- total after '2013-06-04' 2 days don't sum
2013-06-03 -- <- total after '2013-06-03' 1 days don't sum
2013-06-02 -- <- total after '2013-06-02' 0 days don't sum
请帮忙
SELECT
Day_col,
IF (
(SELECT COUNT(Value_col) FROM myTable AS subT WHERE subT.Day_col < t.Day_col) >= 3,
(SELECT SUM(Value_col) FROM myTable AS subT WHERE subT.Day_col < t.Day_col and DATE_ADD(subT.Day_col, INTERVAL 3 DAY) >= t.Day_col),
'--'
) AS total
FROM
myTable t
CREATE TABLE foo
(`Day_col` varchar(10), `Value_col` int)
;
INSERT INTO foo
(`Day_col`, `Value_col`)
VALUES
('2013-06-06', 1),
('2013-06-05', 2),
('2013-06-04', 3),
('2013-06-03', 4),
('2013-06-02', 5)
;
SELECT
Day_col,
IF (
(SELECT COUNT(Value_col) FROM foo AS sf WHERE sf.Day_col < f.Day_col) >= 3,
(SELECT SUM(Value_col) FROM foo AS sf WHERE sf.Day_col >= f.Day_col - INTERVAL 3 DAY and sf.Day_col < f.Day_col),
'--'
) AS total
FROM
foo f;
结果:
DAY_COL TOTAL
2013-06-06 9
2013-06-05 12
2013-06-04 --
2013-06-03 --
2013-06-02 --
为了使查询更整洁,我建议您创建一个简单的函数:
DELIMITER $$
DROP FUNCTION IF EXISTS `getSum`$$
CREATE FUNCTION `getSum`(a DATE) RETURNS INT DETERMINISTIC
BEGIN
DECLARE ret INT DEFAULT 0;
DECLARE ct INT DEFAULT 0;
SELECT COUNT(Day_col), COALESCE(SUM(Value_col),0) INTO ct, ret
FROM YOUR_TABLE WHERE Day_col < a AND Day_col >= DATE_SUB(a,INTERVAL 3 DAY);
IF(ct>=3) THEN RETURN ret;
ELSE RETURN NULL;
END IF;
END$$
DELIMITER ;
然后,只需使用查询:
SELECT Day_col, IF(getSum(Day_col) IS NOT NULL, getSum(Day_col), '--') AS total FROM YOUR_TABLE
或者,如果您要排除“-”天:
SELECT Day_col, getSum(Day_col) AS total FROM YOUR_TABLE WHERE getSum(Day_col) IS NOT NULL
只需将YOUR_TABLE更改为表格的名称即可...
我希望这能帮到您!
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