There are 8,760 hours in a year! (That’s all…)
There is a climate chart that stores temperature data for the area from 1 to 8,760 hours. Now, average daily temperatures throughout the year.
CREATE TABLE #Climate(h INT ,t DECIMAL(18.4));--h: hour t: temperature value
-- there are 8,760 records, corresponding to the temperature of every hour of the year
-- Now, you want to save the average temperature of the whole year by day in table #tD
CREATE TABLE #tD(d INT ,avgt DECIMAL(18.4));-- D: day AVgt: average temperature
The simplest is to use loops
DECLARE @d INT;
DECLARE @h1 INT.@h2 INT;
SET @d = 1;
WHILE @d < = 365
BEGIN
SET @h1 = 24 * (@d - 1);
SET @h2 = @h1 + 24;
Caches calculated values to table variables
INSERT INTO #tD(d,avgt)
SELECT @d
,AVG(t)
FROM [#Climate]
WHERE h BETWEEN @h1 AND @h2;
SET @d = @d + 1;
END --end of @d <= 365
Copy the code
However, there are no advantages to using loops in stored procedures. We can do this with an SQL statement.
The first step is to set up a day table. There are 365 days in a year, and there should be 365 records
CREATE TABLE #days(d INT);
DECLARE @i INT = 1;
WHILE @i < = 365
BEGIN
INSERT INTO #days(d) VALUES(@i);
SET @i = @i + 1;
END
Copy the code
Using this table, we can aggregate
INSERT INTO #tD(d,avgt)
SELECT ds.d
,AVG(c.t)
FROM [#Climate] c,[#days] AS ds
WHERE c.h BETWEEN 24 * (ds.d - 1) AND ds.d * 24
GROUP BY ds.d;
Copy the code
\
\
\