how do I select from another list of selection

Let me explain my question with this example.

I have a df of 2 rows and 1 col called db_list with list of dbs

  1. channels
  2. payment graph history.

and each db contains two tables in df form



  1. Table A
  2. Table B

payment graph history


  1. Table C
  2. Table D

lets say I want to select Table D using this subsetting


Is this the correct way to subset?

It would be easier to understand the structure if you could provide the code to generate a sample db_list.

okay. so I have a list of db as a data frame with one column called db name, and I want to select a db from each list of db, and build SPC_TABLE for each tables in a db. It does this for all db. so two procedures.
At the end of script run, I want to see a list of SPC_TABLE for each db and for all db.
so i ran a 'for loop' twice, first 'for loop' calls the db, 2nd 'for loop' runs SPC_TABLE for each db.
The 2nd 'for loop' for SPC_TABLE works fine , but the first 'for loop' to call a db has been problematic. please assist me and see script below:

for(j in 1:nrow(DB_LIST)){          
                 y=print(paste(w,x, sep = ".")) 
                 z= "SELECT * FROM"
                 # SELECTING DB
                 A=TABLE_LIST[j][,1] #LIST OF TABLE_CATALOGUE
                 B=TABLE_LIST[j][,2] # LIST OF DBO
                 C=TABLE_LIST[j][,3] #LIST OF TABLE_NAME
                 D=print(paste(A,B,C, sep = ".")) # MERGE ALL THREE WITH DOT
                 E= "SELECT * FROM"              # PRINT SELECT * FROM
                 F=print(paste(E,D))             # MERGE 'SELECT * FROM' WITH 'A.B.C'
                 SPC_TABLE[j,1]=  TABLE_LIST[j,1][-c(1,2,4)]
                 SPC_TABLE[j,1]$Count_of_row <- 0
                 SPC_TABLE[j,1]$Count_of_column <- 0
                 for (i in 1:nrow(SPC_TABLE[j])){
                   SPC_TABLE[j,1][i, "Count_of_row"] = nrow(sqlQuery(con,F[i]));
                   SPC_TABLE[j,1][i, "Count_of_column"] = ncol(sqlQuery(con,F[i]));
                 Return SPC_ANALYTICS= list(SPC_TABLE[j,1])

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