How to enforce full integer (no floating point)?
When you define a column as number(m,n) where m is larger than n and n is positive, the values you can store in it can have m-n digits to the left from period and n digits to the right after period. For example when you defined your column as number(5,3), these are valid values: 1,234, 12,345. If you attempt to insert a value with a precision higher than n, it is automatically rounded, for example 1,2345 is rounded to 1,235. 

When you define a column as number(m,0) you can have m digits to the left before the decimal point, and the numbers you insert are automatically rounded.

When you define a column as number(m,n) where n is larger than m, the values you can store in it can have zero digits to the left from the period and n digits to the right from the period with n-m zeros right after the decimal point. For example, if you defined your column as number(3,5), you can have values like 0.00123 in it, but not 0.01200. If you insert the value with more than n digits like 0.001235 it's automatically rounded to 0.00124.

When you define a column as number(m,n) where n is negative then it can store m-n digits to the left from decimal point, there should be exactly abs(n) zeros to the left from the decimal point, and the number is rounded to the last abs(n) places. For example, if you defined your column as number(3,-1), you can store numbers with 3 - -1 = 4 digits before decimal point which should have zeros in the last abs(n)=1 places. You can have values like 280, 1230, and if you isert values with digits other than zero in the last abs(n) places, the numbers are automatically rounded, for example 536 will eventually be stored as 540, 1245 will be stored as 1250.