Any Way To Check If All The Values In A Column Returned Are The Same Value?

say i have a table, and in it are two columns, column1 and column2 and i do the following query:

SELECT column1, column2 FROM table WHERE column2 = '12345'

i want to check if column1 has all the same values, so in the first case, no


column1 column2
------- --------
4 12345
9 12345
5 12345




column1 column2
------- --------
9 12345
9 12345
9 12345


in the 2nd case, column1 contains all the same values, so yes

is there anyway i can check this? i would be doing this in a trigger.. say when a new row is inserted, the value of column1 is inserted, but col 2 is null.. so when they try to fill in the value for col2 of that row, the trigger checks to see if the value they put for col 2 is already in the table.. if it isn't, then everything is ok. but if it is already in teh table, then it checks col1 to see if all the values of col1 are the same

i hope this makes sense

thanks