How to Correctly Retrieve Week Numbers from Dates in SQL?

Retrieve Week Numbers from Dates in SQL

When handling timestamps stored in a non-date format, it becomes necessary to convert them to a recognizable date format for efficient data manipulation. However, users may face challenges when attempting to extract week numbers from converted dates.

Problem: Null Week Number Values

In the given scenario, the user encountered null values when trying to extract week numbers using the following query:

select to_char(to_date(TRANSDATE), 'w') as weekno from tablename;

Solution: Convert to Desired Mask

To retrieve the week number, convert the varchar2 date back to varchar2 with the desired mask:

to_char(to_date('01/02/2012','MM/DD/YYYY'),'WW')

Numerical Week Number

For a numerical week number, wrap the statement in to_number():

to_number(to_char(to_date('01/02/2012','MM/DD/YYYY'),'WW'))

Week Number Parameters

When working with week numbers, consider the following options to suit your specific needs:

• WW: Week of year (1-53), starting with the first day of the year.
• W: Week of month (1-5), starting with the first day of the month.
• IW: Week of year (1-52 or 1-53) based on the ISO standard.

The above is the detailed content of How to Correctly Retrieve Week Numbers from Dates in SQL?. For more information, please follow other related articles on the PHP Chinese website!