# DBI connection examples

The following connection examples are provided for reference.

### Postgres

    con <- DBI::dbConnect(RPostgres::Postgres(),
                          dbname = Sys.getenv("CDM5_POSTGRESQL_DBNAME"),
                          host = Sys.getenv("CDM5_POSTGRESQL_HOST"),
                          user = Sys.getenv("CDM5_POSTGRESQL_USER"),
                          password = Sys.getenv("CDM5_POSTGRESQL_PASSWORD"))

    cdm <- cdm_from_con(con,
                        cdm_schema = Sys.getenv("CDM5_POSTGRESQL_CDM_SCHEMA"),
                        write_schema = Sys.getenv("CDM5_POSTGRESQL_SCRATCH_SCHEMA"))
    DBI::dbDisconnect(con)

### Redshift

Redshift is almost identical to Postgres.

    con <- DBI::dbConnect(RPostgres::Redshift(),
                          dbname   = Sys.getenv("CDM5_REDSHIFT_DBNAME"),
                          host     = Sys.getenv("CDM5_REDSHIFT_HOST"),
                          port     = Sys.getenv("CDM5_REDSHIFT_PORT"),
                          user     = Sys.getenv("CDM5_REDSHIFT_USER"),
                          password = Sys.getenv("CDM5_REDSHIFT_PASSWORD"))

    cdm <- cdm_from_con(con,
                        cdm_schema = Sys.getenv("CDM5_REDSHIFT_CDM_SCHEMA"),
                        write_schema = Sys.getenv("CDM5_REDSHIFT_SCRATCH_SCHEMA"))
    DBI::dbDisconnect(con)

### SQL Server

Using odbc with SQL Server requires driver setup described here. Note, you’ll likely need to download the ODBC Driver for SQL Server.

    con <- DBI::dbConnect(odbc::odbc(),
                          Driver   = "ODBC Driver 18 for SQL Server",
                          Server   = Sys.getenv("CDM5_SQL_SERVER_SERVER"),
                          Database = Sys.getenv("CDM5_SQL_SERVER_CDM_DATABASE"),
                          UID      = Sys.getenv("CDM5_SQL_SERVER_USER"),
                          PWD      = Sys.getenv("CDM5_SQL_SERVER_PASSWORD"),
                          TrustServerCertificate="yes",
                          Port     = 1433)

    cdm <- cdm_from_con(con,
                        cdm_schema = c("tempdb", "dbo"),
                        write_schema =  c("ATLAS", "RESULTS"))
    DBI::dbDisconnect(con)

The connection to SQL Server can be simplified by configuring a DSN. See here for instructions on how to set up the DSN.If we named it “SQL”, our connection is then simplified to.

    con <- DBI::dbConnect(odbc::odbc(), "SQL")
    cdm <- cdm_from_con(con,
                        cdm_schema = c("tempdb", "dbo"),
                        write_schema =  c("ATLAS", "RESULTS"))
    DBI::dbDisconnect(con)

### Snowflake

We can use the odbc package to connect to snowflake.

    con <- DBI::dbConnect(odbc::odbc(),
                              SERVER = Sys.getenv("SNOWFLAKE_SERVER"),
                              UID = Sys.getenv("SNOWFLAKE_USER"),
                              PWD = Sys.getenv("SNOWFLAKE_PASSWORD"),
                              DATABASE = Sys.getenv("SNOWFLAKE_DATABASE"),
                              WAREHOUSE = Sys.getenv("SNOWFLAKE_WAREHOUSE"),
                              DRIVER = Sys.getenv("SNOWFLAKE_DRIVER"))
    cdm <- cdm_from_con(con,
                        cdm_schema =  c("OMOP_SYNTHETIC_DATASET", "CDM53"),
                        write_schema =  c("ATLAS", "RESULTS"))
    DBI::dbDisconnect(con)

Note, as with SQL server we could set up a DSN to simplify this connection as described here for windows and here for macOS.

### Duckdb

Duckdb is an in-process database. We use the duckdb package to connect.

    con <- DBI::dbConnect(duckdb::duckdb(),
                          dbdir=Sys.getenv("CDM5_DUCKDB_FILE"))
    cdm <- cdm_from_con(con,
                        cdm_schema = "main",
                        write_schema = "main")
    DBI::dbDisconnect(con)