There are SAS functions that will return week information from a given date and formats that will group data into week intervals when used with analysis procedures.
You have found one of the week functions but Proc SQL may not group things as you would desire as Week returns a number within a year. So if a customer has records in multiple years you would counting all the visits across the years for that week number.
Here is one approach to getting a count using proc summary:
data have;
input Subscriber_Number $ Date_Email_Sent date9.;
format date_email_sent date9.;
datalines;
19202 03Dec2020
12829 03Dec2020
13455 05Dec2020
13455 05Dec2020
13455 02Dec2020
13455 04Dec2020
;
proc summary data=have nway;
class Subscriber_Number Date_Email_Sent;
format date_email_sent weeku6.;
output out=want;
run;
When you only have class variables the summary will only have _type_ and _freq_ added to the class variables with _freq_ the count of the particular combination. The NWAY option gives you only the combinations that involve all of the class variables.
The dates in this case, since they are so similar all appear as 20W48. 20 is the last two digits of the year and the W tells you the result is a week in the 48th week of the year. Since we used the Weeku format the week is determined using the U algorithm. These formats if using a width larger than 6 start adding more information such day of week which you wouldn't want for this purpose.
If you want a "prettier" result you could make your own custom format. Example:
proc format;
picture myweek (default=9)
low-high = '%Y W %0U' (datatype=date)
;
run;
proc summary data=have nway;
class Subscriber_Number Date_Email_Sent;
format date_email_sent myweek.;
output out=want;
run;
The Picture statement directives, the bits preceded by % allow you to display differing date, time or datetime elements. the %0U says to use the U algorithm for calculating week and the zero that precedes the U displays a zero if the week number is a single digit. Other characters, such as the spaces and the W are used literally. So you could replace W with Week to get values of 2020 Week 48 if desired. The Default indicates how many spaces to display by default. Like other formats you can use a width value, such as Myweek12. for different displayed values.
Caution: If you use double quotes around the target string with directives you will nasty messages about macro variables that aren't defined, so this is one place you really want to use single quotes.
Formats used this way will work in the report procedures like Report and Tabulate to group values if want prettier output than Proc Summary.
proc tabulate data=have;
class Subscriber_Number Date_Email_Sent ;
format date_email_sent myweek.;
table Subscriber_Number* Date_Email_Sent ,
n
;
run;
