Return SQL implementation of operation tree.
to_sql(x, db, ..., source_limit = NULL, indent_level = 0,
tnum = mkTempNameGenerator("tsql"), append_cr = TRUE, using = NULL)
rquery operation tree.
DBI database handle or rquery_db_info object.
generic additional arguments (not used).
numeric if not NULL limit sources to this many rows.
level to indent.
temp sub-query name generator.
logical if TRUE end with CR.
character, if not NULL set of columns used from above.
SQL command