numeric. We can just query with the table name in this view to get the column names and data types of a table in Oracle. Extract value of a single cell: df_name[x, y], where x is the row number and y is the column number of a data frame called df_name. Method 1: ALL_TAB_COLUMNS. Variables in a data frame in R always need to have a name. Alternatively, sqlFetch can fetch the first max rows, in which case sqlFetchMore will retrieve further result rows, provided there has been no other ODBC query on that channel in the meantime. This query fetches a list of all columns in a database without having to specify a table name. If missing, the site names are taken from a column of the data associated with site_layer matching the regular expression ^[Nn]ames{0,1}. So use it with caution. Column names Description. By not specifying the column number, we automatically choose all the columns for row x. (Use attr(x, "row.names") if you need to retrieve an integer-valued set of row names.) If it is an issue with the Microsoft driver, why would RODBC work fine? Row names are currently allowed to be integer or character, but for backwards compatibility (with R <= 2.4.0) row.names will always return a character vector. ALL_TAB_COLUMNS is a view in Oracle that contains the information about all columns in all table. How to Work with Variable Names in R; How to Work with Variable Names in R. By Andrie de Vries, Joris Meys . This can be handy to use if your file doesn’t have a header line, R will use the default variable names V1, V2, …, etc. Query to fetch the colum names and data types character vector of the site names. Better yet, since the underlying operation (remove column in r by name) is very transparent, it will be easy for others to understand your code. Using NULL for the value resets the row names to seq_len(nrow(x)), regarded as ‘automatic’. To access the variable names, you can again treat a data frame like a matrix and use the function colnames() like this: The col.names argument, completed with the c() function that concatenates column names in a vector, specifies the column names in the first row. Return all column names as a list Usage ## S4 method for signature 'DataFrame' columns(x) ## S4 method for signature 'DataFrame' names(x) ## S4 replacement method for signature 'DataFrame' names(x) <- value ## S4 method for signature 'DataFrame' colnames(x) ## S4 replacement method for signature 'DataFrame' colnames(x) <- value colnames(x, do.NULL = TRUE, … Value And R allows us to modify the column names of a data frame by assigning to the array produced by colnames: For instance : df = data.frame(c1=c('a','b'),c2=c(1,2)) > df c1 c2 1 a 1 2 b 2 I would like to retrieve the column name which value is 2 (here, the column is c2) thanks for your help Could the bug be in nanodbc, which is used by … Extract the entire row: df_name[x, ], where x is the row number. col.names can override this default and assign variable names. Rownames and column names are restored as indicated (assuming that they have been placed in the table by the corresponding arguments to sqlSave). However I don't have this issue when using the same database with R package RODBC. Extract the entire column: df_name[, y] where y is The number of fetch vectors to calculate per quadrant (default 9). Hi, I 'd like to know how to retrieve a column name of a data frame. Nonetheless, it worked. site_names. It returns a list of only column names: SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE table_schema = 'db_name' However, when I ran this query in phpmyadmin, it displayed a series of errors. You may also want to look at changing column names to ensure the final results are easy to read. @jimhester I have also the issue on Windows, when using R package odbc with any of the Microsoft drivers: SQL Server', SQL Server Native Client 11.0", ODBC Driver 13 for SQL Server.
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