With the release of dplyr 0.7.0, it is now supposedly easy to connect to Oracle using the odbc package. However, I am running into a problem accessing tables not inside the default schema (for me it is my username). For example, suppose there is the table TEST_TABLE in schema TEST_SCHEMA. Then, example SQL syntax to get data would be: select * from TEST_SCHEMA.TEST_TABLE'.
To do the same in `dplyr, I am trying the following:
# make database connection using odbc: [here's a guide][1]
oracle_con <- DBI::dbConnect(odbc::odbc(), "DB")
# attempt to get table data
tbl(oracle_con, 'TEST_SCHEMA.TEST_TABLE')
Now, this leads to an error message:
Error: <SQL> 'SELECT *
FROM ("TEST_SCHEMA.TEST_TABLE") "zzz12"
WHERE (0 = 1)'
nanodbc/nanodbc.cpp:1587: 42S02: [Oracle][ODBC][Ora]ORA-00942: table or view does not exist
I think the problem here is the double quotation marks, as:
DBI::dbGetQuery(oracle_con, "select * from (TEST_SCHEMA.TEST_TABLE) where rownum < 100;")
works fine.
I struggled with this for a while until I found the solution at the bottom of the introduction to dbplyr. The correct syntax to specify the schema and table combo is:
tbl(oracle_con, in_schema('TEST_SCHEMA', 'TEST_TABLE'))
As an aside, I think the issue with quotation marks is lodged here: https://github.com/tidyverse/dplyr/issues/3080
There are also the following alternate work-arounds that may be suitable depending on what you wish to do. Since the connection used DBI, one can alter the schema via:
DBI::dbSendQuery(oracle_con, "alter session set current_schema = TEST_SCHEMA")
after which tbl(oracle_con, 'TEST_TABLE') will work.
Or, if you have create view privileges, you can create a "shortcut" in your default schema to any table you are interested in:
DBI::dbSendQuery(oracle_con, "CREATE VIEW TEST_TABLE AS SELECT *
FROM TEST_SCHEMA.TEST_TABLE")
Note that the latter may be more suitable for applications where you wish to copy local data to the database for a join, but do not have write access to the table's original schema.
Related
I am new to using SQL Server from RStudio. I am connected to SQL Server from RStudio and the server has several different projects listed in the below image. For this work I am using odbc library. I am trying to retrieve the tables of a specific project(Project_3960). I have tried dbListTables(conn,"Project_3960") but this command retrieve the tables from all the projects listed in the below Picture. I just want to retrieve the table which are listed in dbo in Project_3690.
The first picture is from RStudio and the second picture is from SQL Management Studio to show the structure of the folders, in case for executing SQL Query.
Thanks
Click on the arrow to the left of the dbo object under Project_3690, and it should show you the tables you have access to. If it does not, then you have a permissions problem and will need to talk with the DBA. That allows you to see them via the GUI. In fact, if you don't already know the names of the tables you should be accessing (such as to follow my code below), then this is the easiest, as they are already filtering out the system and other tables that obscure what you need.
To see them in R code, then dbListTables(conn) will show you all tables, including the ones in the Connections pane I just described but also a lot of system and otherwise-internal tables that you don't need. On my SQL Server instance, it returns over 600 tables, so ... you may not want to do just that, but you can look for specific tables.
For example, if you know you should have tables Table_A and Table_B, then you could do
alltables <- dbListTables(conn)
grep("table_", alltables, value = TRUE, ignore.case = TRUE)
to see all of the table names with that string in its name.
If you do not see tables that you know you need to access, then it is likely that your connection code did not include the specific database, in which case you need something like:
conn <- dbConnect(odbc(), database="Project_3690", uid="...", pwd="...",
server="...", driver = "...")
(Most fields should already be in your connection code, don't use literal ... for your strings.)
One can use a system table to find the other tables:
DBI::dbGetQuery(conn, "select * from information_schema.tables where table_type = 'BASE TABLE' and table_schema = 'dbo'")
# TABLE_CATALOG TABLE_SCHEMA TABLE_NAME TABLE_TYPE
# 1 Project_3690 dbo Table_A BASE TABLE
# 2 Project_3690 dbo Table_B BASE TABLE
# 3 Project_3690 dbo Table_C BASE TABLE
(Notional output but representative of what it should look like.)
Its not quite direct to retrieve the data from SQL server using RStudio when you have different schemas and all are connected to the server. It is easy to view the connected Databases with schema in SQL Server Management Studio but not in RStudio. The easiest way while using Rodbc is to use dot(.) operator and its easy to retrieve the tables of a specific data base is by using "." with dbGetQuery function. I tried dbGetQuery(conn, "select * from project_3690.dbo.AE_ISD ") and it works perfectly fine.
I'm trying to use RJDBC to connect to a SAP HANA database and query for a temporary table, which is stored with a #-prefix:
test <- dbGetQuery(jdbcConnection,
"SELECT * FROM #CONTROL_TBL")
# Error in [...]: invalid table name: Could not find table/view #CONTROL_TBL in schema USER
If I execute the SQL statement in HANA, it works perfectly fine. I'm also able to query for permanent tables. Therefore I assume that R doesn't pass over the hashtag. Inserting escapes like "SELECT * FROM \\#CONTROL_TBL" however didn't solve my problem.
It's not possible to query for the data of a local or global temporary table from a different session, since they are by definition session-specific. In the case of a global temporary table one can query for the metadata of the table because they are shared across sessions.
Source: Tutorial for HANA temporary tables
You have to double-quote the table because it contains special characters, see SAP Help, identifiers for details.
test <- dbGetQuery(jdbcConnection,
'SELECT * FROM "#CONTROL_TBL"')
See also related discussion on stackoverflow.
Ok, local temporary tables are always only visible to the session in which they've been defined, while global temporary tables are visible just like normal tables, but the data is session private.
So, if you created the local temp. table (name starts with #) in a different session, then no wonder it cannot be found.
For your example, the question is: why do you need a temporary table in the first place?
Instead of that, you could e.g. define a view or a table function to select data from.
I'm using RJDBC to connect to a local database. This allows me to make SELECT queries easily using dbGetQuery, and CREATE TABLE using dbWriteTable.
However, I cannot figure out a method to DROP TABLE or DELETE or SELECT INTO directly from my R console. These things work when I do it directly in SQL Developer, but not when I pass the query onto the database from R.
How do I perform database record manipulations which are not SELECT statements using R?
I'd try using a different type instead.
dbGetQuery bases itself on finding and iterating over the DB rather than manipulating it's records.
Similar questions were asked before;
I couldn't find a nice R example, but if it helps, A nice java example could be found here:
EDIT:
I found the type I was talking about! Took me a while, anyhow - sqlQuery allows you to run pretty much any query, that is - a change in the DB records. Example I modified from this source:
res <- sqlQuery(con1,"DELETE TABLE TESTDATA", errors=FALSE)
# res will now hold the result of the query.
# -1 means error, otherwise iteration is sucessful, and it will hold the number of rows affected.
if (res == -1){ #if something messed up
cat ("An error has occurred.\n")
msg <- odbcGetErrMsg(con1) #Use your connection for this.
print (msg)
} else {
cat ("Table was deleted successfully.\n")
}
EDIT 2:
I got it confused with RODBC, however there's no reason to worry, since I found the RJDBC alternative as well! It's called, dbSendUpdate. Example:
# Assuming you have the connection saved as conn; these example shows how to use dbSendUpdate to create tables and insert values.
# You could use it with every non-selective query, that is, which manipulates the record (update,delete,insert,drop etc.)
# create table, with dbSendUpdate:
dbSendUpdate(conn, "CREATE TABLE foo(a INT,b VARCHAR(100))")
# insert value, bind parameters to placeholders in statement:
dbSendUpdate(conn, "INSERT INTO foo VALUES(?,?)", 42, "bar")
# feel free to modify the query itself, these are just example values.
this is similar to another answered question here
basically dbGetQuery() as it name implies is used to send queries and recive their result.
if you want to send a general statement to the db like 'drop table' etc.
you can use:
dbSendUpdate(connection_object, "drop table table_name")
I am getting this error while saving my data into the table. I have already created a 'product_Design' table in my database. I am using Sql Server 2008. Everything is working fine on local host but not on the server. I also tried to insert data in different tables and its working but I am just not able to insert data in this(product_Design) table ? I really need help regarding this thing.
here is my sql query
insert into z3ctjholo.dbo.product_Design values(#prodID, #productName, #designName, #designPath, #finalDesign, #front, #cont, #divHeight, GETDATE(), 0, 1)
I also tried this query
insert into product_Design values(#prodID, #productName, #designName, #designPath, #finalDesign, #front, #cont, #divHeight, GETDATE(), 0, 1)
Both the queries are generating error. Please help me out.
Thanks..
So finally i found what is the problem. if you ever face such kind of problem then execute this command in sql server and see whether your table is connected to any schema apart from dbo. Use this statement to check whether the table is connected to any other schema.
use yourDatabaseName
Then
SELECT * FROM INFORMATION_SCHEMA.TABLES
after that if you find that your table is connected with other schema apart from dbo then use your any statement like this
select * from schemaName.tableName
(eg. my schema name is z3ctjholo and my table name is product_Design)
so my statement would be like this
select * from z3ctjholo.product_Design
what i was doing wrong, i was using two schema names (z3ctjholo.dbo.product_Design).
I hope it will help someone..
Thanks...
There are two reasons, I can find so far.
1. Either the connection settings in web.config is incorrect.
2. your database is case sensitive collation and so check the name with case. May be you have created the table with name Product_Design and trying to insert in product_Design, in this case also, the command may not work.
Please check both the points.
I am trying to connect to a table that is not in the sys schema. The code below works if sys.tablea exists.
conn <- dbConnect(dbDriver("MonetDB"), "monetdb://localhost/demo")
frame <- monet.frame(conn,"tablea")
If I define tablea in a different schema, e.g. xyz.tablea, then I get the error message
Server says 'SELECT: no such table 'tablea'' [#NA]
The account used to connect has rights to the table.
In a related question, is it possible to use camel-case from MonetDB.R? When I change the table name to TableA, the server again responds with
Server says 'SELECT: no such table 'tablea'' [#NA]
where the table name is all lower-case.
Using tables in other schemata is not possible with the current constructor of monet.frame. However, you can work around the issue as follows:
frame <- monet.frame(conn,"select * from xyz.tablea")
This trick also works with CamelCased table names.
For the next version, I am planning to fix the issue.