How to Get the Week Number from a Date Column in SQL?

How to Extract Week Number in SQL

Issue

You have a column with dates in a specific format (MM/DD/YYYY), and you're unable to retrieve the week number. The to_char(to_date(TRANSDATE), 'w') query returns null values.

Solution

To extract the week number, follow these steps:

1. Convert the VARCHAR2 date to a true DATE datatype using TO_DATE().

   TO_DATE('01/02/2012', 'MM/DD/YYYY')

2. Convert the DATE back to a VARCHAR2 with the desired mask:

   TO_CHAR(TO_DATE('01/02/2012', 'MM/DD/YYYY'), 'WW')

   This will return the week number of the year, starting from 1 for the first week.

Additional Week Number Options

In addition to 'WW', there are other parameters you can use to extract week numbers:

• 'W': Week of the month, starting from 1.
• 'IW': ISO week of the year, starting from 1 or 53.

Example usage:

-- Week of the month
TO_CHAR(TO_DATE('01/02/2012', 'MM/DD/YYYY'), 'W')

-- ISO week of the year
TO_CHAR(TO_DATE('01/02/2012', 'MM/DD/YYYY'), 'IW')

The above is the detailed content of How to Get the Week Number from a Date Column in SQL?. For more information, please follow other related articles on the PHP Chinese website!