Description Usage Arguments Value Author(s) See Also Examples
View source: R/easyrodbcexcel.R
Send and retrieve a query in a SQLIte database (referenced by 'edb').
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edb |
An object of class 'edb', such as returned by |
statement |
Single character string. SQL statement / SQL query to be passed to |
formatCol |
If not NULL, a named list of functions to be applied to certain columns after the data has been extracted from the database. The name of each list item gives the column to process, and the value of each item gives the function that must be applied. For instance formatCol = list("DATE"=as.Date) will apply the function as.Date to the column "DATE". |
testFiles |
Single logical. Should the function test for the presence (file.exist()) of the needed files in the folder before trying to fetch information from the database? |
readOnly |
Single logical. If as read only. See
|
verbose |
Single logical. If TRUE, information on what is done are output on screen. |
... |
Additional parameters to be passed to |
The function returns the requested table.
Julien MOEYS <Julien.Moeys@mark.slu.se>
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# System check. Ingnore this or set 'testODBC' to TRUE
testODBC <- (class(try(odbcDataSources())) != "try-error") & # Check (R)ODBC
(Sys.info()[[ "sysname" ]] == "Windows") & # Only MS Windows
(.Machine$"sizeof.pointer" == 4) # Only 32-bits
### Windows only:
if( testODBC ){
### Make a copy of Excel example file:
# (a database of soil profile description)
file.copy(
from = system.file( "soils.xls", package = "easyrodbcexcel" ),
to = "soils.xls"
)
# soils.xls is now in your working directory.
library( "RODBC" ) # Because soils.db is a SQLite database...
### Describe the database (NB: this is not a connection)
myDb <- edb( dbType = "RODBC_Excel", dbName = "soils.xls" )
### Use the database:
## Read data in a table in the database
# Retrieve a table (data.frame style subsetting):
myDb[ "WRB_SOIL_GROUP" ]
# Same operation, but with edbRead()
edbRead( edb = myDb, tableName = "WRB_SOIL_GROUP" )
# Retrieve part of a table (with row constrains)
myDb[ "WRB_SOIL_GROUP", list("ABBREV" = c("AC","CR","PL")),
verbose = TRUE ]
# Same operation, but with edbQuery()
edbQuery( edb = myDb, statement =
"SELECT * FROM [WRB_SOIL_GROUP] WHERE [ABBREV] IN ('AC','CR','PL')" )
### Clean-up
file.remove( "soils.xls" )
### Access 2007 ---------------------------------------------
file.copy(
from = system.file( "soils.xlsx", package = "easyrodbcexcel" ),
to = "soils.xlsx"
)
# soils.db is now in your working directory.
library( "RODBC" ) # Because soils.db is a SQLite database...
### Describe the database (NB: this is not a connection)
myDb2 <- edb( dbType = "RODBC_Excel", dbName = "soils.xlsx",
excelVersion = 2007 )
### Use the database:
## Read data in a table in the database
# Retrieve a table (data.frame style subsetting):
myDb2[ "WRB_SOIL_GROUP" ]
# Same operation, but with edbRead()
edbRead( edb = myDb2, tableName = "WRB_SOIL_GROUP" )
# Retrieve part of a table (with row constrains)
myDb2[ "WRB_SOIL_GROUP", list("ABBREV" = c("AC","CR","PL")),
verbose = TRUE ]
# Same operation, but with edbQuery()
edbQuery( edb = myDb2, statement =
"SELECT * FROM [WRB_SOIL_GROUP] WHERE [ABBREV] IN ('AC','CR','PL')" )
### Clean-up
file.remove( "soils.xlsx" )
} #
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