Date Manipulation Functions
Description
This article discusses essential date manipulation functions in Spark SQL, including getting current dates and timestamps, date arithmetic, truncating and date_trunc functions, extracting information using date_format, working with calendar functions, and dealing with Unix timestamps.
Explanation for the video
The video embedded in this article complements the text by providing visual demonstrations and explanations of the concepts discussed. It is recommended to watch the video alongside reading the text for a better understanding.
Key Concepts Explanation
Getting Current Date and Timestamp
The current_date
function returns today’s date, while current_timestamp
provides the current timestamp. These functions do not require ()
and follow specific formats.
SELECT current_date AS current_date
SELECT current_timestamp AS current_timestamp
Date Arithmetic
Functions like date_add
, date_sub
, datediff
, and add_months
help perform date calculations. For instance:
SELECT date_add(current_date, 32) AS result
SELECT datediff('2019-03-30', '2017-12-31') AS result
Beginning Date or Time - trunc and date_trunc
Using trunc
and date_trunc
, you can get the starting date or time for a given period, like the beginning of a month or year. Note that date_trunc
can handle timestamps with more precision.
SELECT trunc(current_date, 'MM') AS beginning_date_month
SELECT date_trunc('HOUR', current_timestamp) AS hour_beginning
Extracting information using date_format
The date_format
function extracts date/time information, such as year, month, day, and time components, from timestamps or dates.
SELECT date_format(current_timestamp, 'yyyy') AS year
SELECT date_format(current_timestamp, 'MM') AS month
Extracting information - Calendar functions
Functions like day
, month
, weekofyear
, etc., provide individual date components from dates or timestamps for specific calculations.
SELECT year(current_date) AS year
SELECT month(current_date) AS month
Dealing with Unix Timestamp
Functions like from_unixtime
and to_unix_timestamp
help in converting between Unix timestamps and regular timestamps. For instance:
SELECT from_unixtime(1556662731) AS timestamp
SELECT to_unix_timestamp('2019-04-30 18:18:51') AS unixtime
Hands-On Tasks
Explore the date manipulation functions mentioned in the article. Conduct the following tasks:
- Use
current_date
andcurrent_timestamp
functions to get today’s date and current time. - Utilize
date_add
anddatediff
to perform arithmetic on dates. - Experiment with
trunc
anddate_trunc
to find the beginning date or time. - Extract date information using
date_format
for different formats. - Use calendar functions like
year
,month
,weekofyear
, etc., to extract date components. - Try converting between regular timestamps and Unix timestamps using
from_unixtime
andto_unix_timestamp
.
Conclusion
In summary, this article delves into the essential date manipulation functions in Spark SQL, covering a wide range of operations from getting current dates and times to dealing with Unix timestamps. Practice and experiment with these functions to enhance your understanding and proficiency in date calculations.
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