SQL SELECT Statement

My table looks like this -

EFF_DATE    ID         Col_A  Col_B Col_C
01/01/1900  1122334    N      N     N
12/01/2010  1122334    NULL   Y     Y
12/02/2010  1122334    Y      NULL  NULL
12/21/2010  1122334    NULL   NULL  NULL
01/01/1900  44555222   N      N     N
12/02/2010  44555222   NULL   NULL  NULL
01/01/1900  897969595  N      N     N
11/22/2010  897969595  Y      NULL  NULL
01/01/1900  897969596  N      N     N
11/22/2010  897969596  Y      NULL  NULL

Now, I need to populate all the columns for every record such that if for a date Col_A is NULL, it should populate the the value of Col_A for the same Id from the previous eff_date.

This is the solution I want -

EFF_DATE    ID  Col_A   Col_B   Col_C
01/01/1900  01122334    N   N   N
12/01/2010  01122334    N   Y   Y
12/02/2010  01122334    Y   Y   Y
12/21/2010  01122334    Y   Y   Y
01/01/1900  044555222   N   N   N
12/02/2010  044555222   N   N   N
01/01/1900  897969595   N   N   N
11/22/2010开发者_StackOverflow中文版  897969595   Y   N   N
01/01/1900  897969596   N   N   N
11/22/2010  897969596   Y   N   N

Please help! I want to use simple SELECT statement to achieve this result.

in mysql

UPDATE tbL_table 
JOIN (SELECT EFF_DATE, COl_A, @x:=@x+1 AS rnum FROM tbl_table) a ON a.EFF_DATE=tbl_table.EFF_DATE
JOIN (SELECT EFF_DATE, COl_A, @y:=@y+1 AS rnum FROM tbl_table) b ON b.rnum+1=a.rnum 
JOIN (SELECT @x:=0, @y:=0) as vars on true 
SET Col_A=IF(Col_A IS NULL, b.Col_A , Col_A)

You'll need to order by eff_date somehow but thats the basic idea of how I would do it.