is-empty

I have a table and the columns on this table contains empty spaces for some records. Now I need to move the data to another table and replace the empty spaces with a NULL value. I tried to use: REPLACE(ltrim(rtrim(col1)),' ',NULL) but it doesn't work. It will convert all of the values of col1 to NULL . I just want to convert only those values that have empty spaces to NULL . Did you try this? UPDATE table SET col1 = NULL WHERE col1 = '' As the commenters point out, you don't have to do ltrim() or rtrim() , and NULL columns will not match '' . I solved a similar problem using NULLIF function:

ILSpy shows that String.IsNullOrEmpty is implemented in terms of String.Length . But then why is String.IsNullOrEmpty(s) faster than s.Length == 0 ? For example, it's 5% faster in this benchmark: var stopwatches = Enumerable.Range(0, 4).Select(_ => new Stopwatch()).ToArray(); var strings = "A,B,,C,DE,F,,G,H,,,,I,J,,K,L,MN,OP,Q,R,STU,V,W,X,Y,Z,".Split(','); var testers = new Func<string, bool>[] { s => s == String.Empty, s => s.Length == 0, s => String.IsNullOrEmpty(s), s => s == "" }; int count = 0; for (int i = 0; i < 10000; ++i) { stopwatches[i % 4].Start(); for (int j = 0; j < 1000; ++j)

How do I detect empty cells in a cell array? I know the command to remove the empty cell is a(1) = [] , but I can't seem to get MATLAB to automatically detect which cells are empty. Background: I preallocated a cell array using a=cell(1,53) . Then I used if exist(filename(i)) and textscan to check for a file, and read it in. As a result, when the filename(i) does not exist, an empty cell results and we move onto the next file. When I'm finished reading in all the files, I would like to delete the empty cells of a . I tried if a(i)==[] Use CELLFUN %# find empty cells emptyCells = cellfun(

I'd like to check if variable is None or numpy.array. I've implemented check_a function to do this. def check_a(a): if not a: print "please initialize a" a = None check_a(a) a = np.array([1,2]) check_a(a) But, this code raises ValueError. What is the straight forward way? ValueError Traceback (most recent call last) <ipython-input-41-0201c81c185e> in <module>() 6 check_a(a) 7 a = np.array([1,2]) ----> 8 check_a(a) <ipython-input-41-0201c81c185e> in check_a(a) 1 def check_a(a): ----> 2 if not a: 3 print "please initialize a" 4 5 a = None ValueError: The truth value of an array with more than

I have a data frame where all the variables are of character type. Many of the columns are completely empty, i.e. only the variable headers are there, but no values. Is there any way to subset out the empty columns? If your empty columns are really empty character columns, something like the following should work. It will need to be modified if your "empty" character columns include, say, spaces. Sample data: mydf <- data.frame( A = c("a", "b"), B = c("y", ""), C = c("", ""), D = c("", ""), E = c("", "z") ) mydf # A B C D E # 1 a y # 2 b z Identifying and removing the "empty" columns. mydf[