make.db.names: Make R/Splus identifiers into legal SQL identifiers

Description

Produce legal SQL identifiers from a character vector.

Usage

make.db.names(dbObj, snames, keywords, unique=TRUE, allow.keywords=TRUE, ...)
  SQLKeywords(dbObj, ...)
  isSQLKeyword(dbObj, name, keywords=.SQL92Keywords, 
                  case=c("lower", "upper", "any")[3], ...)

Arguments

dbObj

any DBI object (e.g., DBIDriver).

snames

a character vector of R/Splus identifiers (symbols) from which we need to make SQL identifiers.

name

a character vector with database identifier candidates we need to determine whether they are legal SQL identifiers or not.

unique

logical describing whether the resulting set of SQL names should be unique. Its default is TRUE. Following the SQL 92 standard, uniqueness of SQL identifiers is determined regardless of whether letters are upper or lower case.

allow.keywords

logical describing whether SQL keywords should be allowed in the resulting set of SQL names. Its default is TRUE

keywords

a character vector with SQL keywords, by default it's .SQL92Keywords defined by the DBI.

case

a character string specifying whether to make the comparison as lower case, upper case, or any of the two. it defaults to any.

...

any other argument are passed to the driver implementation.

Value

make.db.names returns a character vector of legal SQL identifiers corresponding to its snames argument. SQLKeywords returns a character vector of all known keywords for the database-engine associated with dbObj.
isSQLKeyword returns a logical vector parallel to name.

Bugs

The current mapping is not guaranteed to be fully reversible: some SQL identifiers that get mapped into S identifiers with make.names and then back to SQL with make.db.names will not be equal to the original SQL identifiers (e.g., compound SQL identifiers of the form username.tablename will loose the dot ``.'').

Details

The algorithm in make.db.names first invokes make.names and then replaces each occurrence of a dot ``.'' by an underscore ``_''. If allow.keywords is FALSE and identifiers collide with SQL keywords, a small integer is appended to the identifier in the form of "_n".

The set of SQL keywords is stored in the character vector .SQL92Keywords and reflects the SQL ANSI/ISO standard as documented in "X/Open SQL and RDA", 1994, ISBN 1-872630-68-8. Users can easily override or update this vector.

References

See the Database Interface definition document DBI.pdf in the base directory of this package or http://developer.r-project.org/db.

Examples

Run this code

# This example shows how we could export a bunch of data.frames
# into tables on a remote database.

con <- dbConnect("Oracle", user="iptraffic", pass = pwd)

export <- c("trantime.email", "trantime.print", "round.trip.time.email")
tabs <- make.db.names(export, unique = T, allow.keywords = T)

for(i in seq(along = export) )
   dbWriteTable(con, name = tabs[i],  get(export[i]))

# Oracle's extensions to SQL keywords
oracle.keywords <- c("CLUSTER", "COLUMN", "MINUS", "DBNAME")
isSQLKeyword(nam, c(.SQL92Keywords, oracle.keywords))
[1]  T  T  T  F

Run the code above in your browser using DataLab

Last chance! 50% off unlimited learning