Use the following instead:
DATE_FORMAT(`datetime_added`,'%Y-%m')
Explanation:
DATE_FORMAT() function lets you format the date anyway you like using specifiers described in the table below (taken verbatim from documentation). So a format string '%Y-%m' means: “A full year (4 digits), followed by a dash (-), followed by a two-digit month number”.
Note that you can specify the language used for day/month names by setting lc_time_names system variable. Extremely useful. Refer to documentation for more details.
| Specifier | Description |
|---|---|
| %a | Abbreviated weekday name (Sun..Sat) |
| %b | Abbreviated month name (Jan..Dec) |
| %c | Month, numeric (0..12) |
| %D | Day of the month with English suffix (0th, 1st, 2nd, 3rd, …) |
| %d | Day of the month, numeric (00..31) |
| %e | Day of the month, numeric (0..31) |
| %f | Microseconds (000000..999999) |
| %H | Hour (00..23) |
| %h | Hour (01..12) |
| %I | Hour (01..12) |
| %i | Minutes, numeric (00..59) |
| %j | Day of year (001..366) |
| %k | Hour (0..23) |
| %l | Hour (1..12) |
| %M | Month name (January..December) |
| %m | Month, numeric (00..12) |
| %p | AM or PM |
| %r | Time, 12-hour (hh:mm:ss followed by AM or PM) |
| %S | Seconds (00..59) |
| %s | Seconds (00..59) |
| %T | Time, 24-hour (hh:mm:ss) |
| %U | Week (00..53), where Sunday is the first day of the week; WEEK() mode 0 |
| %u | Week (00..53), where Monday is the first day of the week; WEEK() mode 1 |
| %V | Week (01..53), where Sunday is the first day of the week; WEEK() mode 2; used with %X |
| %v | Week (01..53), where Monday is the first day of the week; WEEK() mode 3; used with %x |
| %W | Weekday name (Sunday..Saturday) |
| %w | Day of the week (0=Sunday..6=Saturday) |
| %X | Year for the week where Sunday is the first day of the week, numeric, four digits; used with %V |
| %x | Year for the week, where Monday is the first day of the week, numeric, four digits; used with %v |
| %Y | Year, numeric, four digits |
| %y | Year, numeric (two digits) |
| %% | A literal % character |
| %x | x, for any “x” not listed above |