in microsoft excell , what I should do that the entries in the single column are not repeated?

What I do to eliminate duplicate rows.

Its simple: I first sort to put all the same values together and then check for duplicates with an "=IF( A2=a1,1,"") formula and then delete the rows that have been marked as duplicates.

1. First of all, "no entry repeated" is not exactly defined. Is Rat, rat and RAT three different words or not?

Is 10.00 the same as 10? How about 123 Elm Street and 123 Elm St. ? Or "a b c" and "ab c" or "a b c "?

Excel can only determine equivalence for exact matches "A" is not the same as " A" or "A " nor is "11" the same as 11. You can convert text to numbers and vice versa and you can convert upper case to lower or vice versa easily. ********* out spaces and other non printing characters is more time consuming. And expanding abbreviations (or abbreviating) can be very time consuming.

== so lets assume that the cells are either exactly the same (repeated) or are different ==

2. If order matters (sequence) then you should add a column with the number of the row 1,2,3,...,5000

(Two ways to do that: in a new column number the first couples and drag and copy that or (an older way) number first cell in column 1, enter formula in cell below that as =1+<↑> (where<↑> means cell above it), and copy that down to bottom of entries. Then highlight that column and copy the value onto itself. (changing it from formulas to the numbers ...Copy...Paste Special...Value)

3. Now the easiest step: sort on the column you don't want repeats in. Be sure to include all of the data and not just that one column. If you sort on that column first and then the numbered column second the entries will keep a relative sequence...(this would be with only one sort operation and NOT two separate sorts - I'm not sure how familiar you are with excel...)

4. Next in a new column (yes another one) enter this formula in each row except the top row:

= if(A2=A1,1,"") (this is assuming that the column of interest is column A and it starts at A1 -- you'll have to change this formula to suit your sheet) This IF statement will compare the contents of two adjacent cells and return a 1 if they are the same and will return nothing (quote-quote) if they are different.

5. Copy this formula down to the last entry row.

6. Change it from a formula to a value, as above.

7. Now all repeats are marked. You've got your choice: get rid of them or sort them down to the bottom of the column. Sorting them down allows you to take a look at them before you delete them. All you do to sort them is to sort all the data using that "repeat" column (1's or nothing)

8. What I usually do at this point instead is to filter on that column and select nonblanks (If you have the horrible Excel 2007, my condolences and filter on 1). After I filter I carefully delete all of the rows (excepting the top row - be careful!) n the filtered region. As long as you know that even if the top row is NOT a repeat it still shows up you'll be ok. Anyway to delete just highlight the row numbers and delete the rows.

9. Finally (turn off the filter if you used it) resort on the numbered column and then, if you want delete it, leaving you with only the columns you started with - oh delete the "repeat column - altough it shouldn't have any entries if you did it right.

/ Ex: =A1/A2 divides a number in A1 by a number in A2 giving the result in the cell of the formula