How do I put days of the week in order...Monday, Tuesday, Wednesday, etc.?
If you want to order by the day of the week, then just order by column which contains the date. For testing purposes, I've set up a little test table which contains only one column (DAY). Below is a query which shows the contents of that column:
SQL> select day,to_char(day,'DAY') from test; DAY TO_CHAR(D --------- --------- 01-MAY-01 TUESDAY 02-MAY-01 WEDNESDAY 03-MAY-01 THURSDAY 04-MAY-01 FRIDAY 05-MAY-01 SATURDAY 06-MAY-01 SUNDAY 07-MAY-01 MONDAY 08-MAY-01 TUESDAY 09-MAY-01 WEDNESDAY 10-MAY-01 THURSDAY
Now, they were inserted into this table in sorted order. So let's see how to put them in *reverse* order!
SQL> select day,to_char(day,'DAY') from test 2 order by day desc; DAY TO_CHAR(D --------- --------- 10-MAY-01 THURSDAY 09-MAY-01 WEDNESDAY 08-MAY-01 TUESDAY 07-MAY-01 MONDAY 06-MAY-01 SUNDAY 05-MAY-01 SATURDAY 04-MAY-01 FRIDAY 03-MAY-01 THURSDAY 02-MAY-01 WEDNESDAY 01-MAY-01 TUESDAY
Notice that the days of the week go into reverse order now! I've just used the ORDER BY clause on the column of DATE datatype.
If you want to group all of the "Tuesdays" together, then you'll have to order by the TO_CHAR column as can be seen in the following example:
SQL> select day,to_char(day,'DAY') from test 2 order by 2; DAY TO_CHAR(D --------- --------- 04-MAY-01 FRIDAY 07-MAY-01 MONDAY 05-MAY-01 SATURDAY 06-MAY-01 SUNDAY 03-MAY-01 THURSDAY 10-MAY-01 THURSDAY 01-MAY-01 TUESDAY 08-MAY-01 TUESDAY 02-MAY-01 WEDNESDAY 09-MAY-01 WEDNESDAY
Notice that all of the Wednesday's are together, etc. But if you want this sorted further so that all of the Monday's fall before the Tuesday's, then you'll need one more trick. You'll have to use the TO_CHAR function again, but this time, get the day of the week as a number. For instance, see below:
SQL> select day,to_char(day,'DAY'),to_char(day,'D') from test 2 order by to_char(day,'D'); DAY TO_CHAR(D T --------- --------- - 06-MAY-01 SUNDAY 1 07-MAY-01 MONDAY 2 01-MAY-01 TUESDAY 3 08-MAY-01 TUESDAY 3 02-MAY-01 WEDNESDAY 4 09-MAY-01 WEDNESDAY 4 03-MAY-01 THURSDAY 5 10-MAY-01 THURSDAY 5 04-MAY-01 FRIDAY 6 05-MAY-01 SATURDAY 7
Notice now that all of the Tuesday's fall before the Wednesday's, etc.
I wasn't sure which way you wanted to sort your data so that is why I gave you three examples. Hopefully, one of these fit the bill!!
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This was first published in May 2001