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sql server - how to query specific time - T SQL
I have a timestamp field.
I need to query all the records for the hour.. A record for 1,2,3 o'clock.
The data looks like
2012-11-01 01:00:00
2012-11-01 01:15:00
2012-11-01 01:45:00
2012-11-01 02:00:00
2012-11-01 02:15:00
2012-11-01 03:00:00
How do query for the full hour?
I need to query all the records for the hour.. A record for 1,2,3 o'clock.
The data looks like
2012-11-01 01:00:00
2012-11-01 01:15:00
2012-11-01 01:45:00
2012-11-01 02:00:00
2012-11-01 02:15:00
2012-11-01 03:00:00
How do query for the full hour?
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This will give you the basic structure of the query:
select * from your_table
where column_name between convert(datetime, '2012-11-01 01:00:00', 120) and convert(datetime, '2012-11-01 02:00:00', 120)
select * from your_table
where column_name between convert(datetime, '2012-11-01 01:00:00', 120) and convert(datetime, '2012-11-01 02:00:00', 120)
Just so you understand, a TimeStamp field is not the same as a Date/Time field. According to Microsoft:
"It is used as a mechanism for version-stamping table rows. The storage size is 8 bytes. The timestamp data type is just an incrementing number and does not preserve a date or a time. To record a date or time, use a datetime data type."
"It is used as a mechanism for version-stamping table rows. The storage size is 8 bytes. The timestamp data type is just an incrementing number and does not preserve a date or a time. To record a date or time, use a datetime data type."
Most important are:
1) not to perform any function on the column itself
2) not to count the same row more than once
I strongly recommend the style below for ALL date/datetime checks:
--query for 1AM rows only
WHERE
datetime_column >= '20121101 01:00:00' AND
datetime_column < '20121101 02:00:00'
Leaving out the dashes prevents any conversion errors ('YYYYMMDD' is always interpreted correctly) and/or misunderstandings about what the date value represents.
Using >= and < rather than between avoids counting rows on the exact hour twice.
1) not to perform any function on the column itself
2) not to count the same row more than once
I strongly recommend the style below for ALL date/datetime checks:
--query for 1AM rows only
WHERE
datetime_column >= '20121101 01:00:00' AND
datetime_column < '20121101 02:00:00'
Leaving out the dashes prevents any conversion errors ('YYYYMMDD' is always interpreted correctly) and/or misunderstandings about what the date value represents.
Using >= and < rather than between avoids counting rows on the exact hour twice.
But I have many dates!
What about this...
First
SUBSTRING( CONVERT(nvarchar(30), TIMESTAMP, 120),15,5) AS DT
then
select .... WHERE DT = '00:00'
What about this...
First
SUBSTRING( CONVERT(nvarchar(30), TIMESTAMP, 120),15,5) AS DT
then
select .... WHERE DT = '00:00'
If you just want to group a lot of rows by their hours only, ignoring dates, do as below.
Yes, it uses a function on the column, but when you want all values you have to:
SELECT
HOUR(TIMESTAMP) AS HR,
...
FROM dbo.tablename
--OPTIONAL!: for example, all records for current year only
--WHERE
--TIMESTAMP >= '20120101' AND TIMESTAMP < '20130101'
GROUP BY
HOUR(TIMESTAMP)
ORDER BY
HOUR(TIMESTAMP)
If you want to see days, but only one row per hour per day, you can do this:
SELECT
DATEADD(HOUR, DATEDIFF(HOUR, 0, TIMESTAMP), 0) AS DT,
...
FROM dbo.tablename
--OPTIONAL!: for example, all records for current year only
--WHERE
--TIMESTAMP >= '20120101' AND TIMESTAMP < '20130101'
GROUP BY
DATEADD(HOUR, DATEDIFF(HOUR, 0, TIMESTAMP), 0)
ORDER BY
DATEADD(HOUR, DATEDIFF(HOUR, 0, TIMESTAMP), 0)
Yes, it uses a function on the column, but when you want all values you have to:
SELECT
HOUR(TIMESTAMP) AS HR,
...
FROM dbo.tablename
--OPTIONAL!: for example, all records for current year only
--WHERE
--TIMESTAMP >= '20120101' AND TIMESTAMP < '20130101'
GROUP BY
HOUR(TIMESTAMP)
ORDER BY
HOUR(TIMESTAMP)
If you want to see days, but only one row per hour per day, you can do this:
SELECT
DATEADD(HOUR, DATEDIFF(HOUR, 0, TIMESTAMP), 0) AS DT,
...
FROM dbo.tablename
--OPTIONAL!: for example, all records for current year only
--WHERE
--TIMESTAMP >= '20120101' AND TIMESTAMP < '20130101'
GROUP BY
DATEADD(HOUR, DATEDIFF(HOUR, 0, TIMESTAMP), 0)
ORDER BY
DATEADD(HOUR, DATEDIFF(HOUR, 0, TIMESTAMP), 0)
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