Unquote identifiers
Call this method to convert a SQL object created by dbQuoteIdentifier()
back to a list of Id objects.
dbUnquoteIdentifier(conn, x, ...)
conn |
A DBIConnection object, as returned by
|
x |
|
... |
Other arguments passed on to methods. |
dbUnquoteIdentifier() returns a list of objects
of the same length as the input.
For an empty character vector this function returns a length-0 object.
The names of the input argument are preserved in the output.
When passing the first element of a returned object again to
dbUnquoteIdentifier() as x
argument, it is returned unchanged (but wrapped in a list).
Passing objects of class Id should also return them unchanged (but wrapped in a list).
(For backends it may be most convenient to return Id objects
to achieve this behavior, but this is not required.)
An error is raised if plain character vectors are passed as the x
argument.
For any character vector of length one, quoting (with dbQuoteIdentifier())
then unquoting then quoting the first element is identical to just quoting.
This is also true for strings that
contain special characters such as a space,
a dot,
a comma,
or quotes used to mark strings
or identifiers,
if the database supports this.
Unquoting simple strings (consisting of only letters) wrapped with SQL()
and then quoting via dbQuoteIdentifier() gives the same result as just
quoting the string.
Similarly, unquoting expressions of the form SQL("schema.table")
and then quoting gives the same result as quoting the identifier
constructed by Id(schema = "schema", table = "table").
Other DBIResult generics:
DBIResult-class,
dbBind(),
dbClearResult(),
dbColumnInfo(),
dbFetch(),
dbGetInfo(),
dbGetRowCount(),
dbGetRowsAffected(),
dbGetStatement(),
dbHasCompleted(),
dbIsReadOnly(),
dbIsValid(),
dbQuoteIdentifier(),
dbQuoteLiteral(),
dbQuoteString()
# Unquoting allows to understand the structure of a
# possibly complex quoted identifier
dbUnquoteIdentifier(
ANSI(),
SQL(c('"Catalog"."Schema"."Table"', '"Schema"."Table"', '"UnqualifiedTable"'))
)
# The returned object is always a list,
# also for Id objects
dbUnquoteIdentifier(
ANSI(),
Id(catalog = "Catalog", schema = "Schema", table = "Table")
)
# Quoting is the inverse operation to unquoting the elements
# of the returned list
dbQuoteIdentifier(
ANSI(),
dbUnquoteIdentifier(ANSI(), SQL("UnqualifiedTable"))[[1]]
)
dbQuoteIdentifier(
ANSI(),
dbUnquoteIdentifier(ANSI(), Id(schema = "Schema", table = "Table"))[[1]]
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