🗄️ R Database Integration – Connect R with MySQL, SQLite, PostgreSQL

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🧲 Introduction – Connecting R to Databases

R is not just limited to flat files like CSVs—it also integrates seamlessly with relational databases such as MySQL, PostgreSQL, SQLite, and SQL Server. Using R’s database interface, you can connect, query, and manipulate structured data from live systems directly inside your R script or notebook.

🎯 In this guide, you’ll learn:

• How to connect R to a database
• Use the DBI and RMySQL/RSQLite packages
• Execute SQL queries and retrieve results
• Best practices for closing connections and securing credentials

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📦 Required Packages for DB Integration

Database	R Package
SQLite	RSQLite
MySQL/MariaDB	RMySQL or RMariaDB
PostgreSQL	RPostgres
Generic SQL	DBI

Install core packages:

install.packages("DBI")
install.packages("RSQLite")      # For SQLite
# install.packages("RMySQL")    # For MySQL (may need system libs)

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🧱 1. Connect to a SQLite Database

library(DBI)
con <- dbConnect(RSQLite::SQLite(), dbname = "my_database.sqlite")

🔍 Explanation:

• dbConnect() creates a live connection to the SQLite file.
• The connection object con is used for running SQL queries.

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📤 2. Create a Table and Insert Data

dbWriteTable(con, "students", data.frame(
  Name = c("Alice", "Bob"),
  Age = c(23, 24)
))

🔍 Explanation:

• dbWriteTable() creates a new table and fills it with data from a data frame.
• Table students is now part of your SQLite database.

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📥 3. Query Data with SQL

result <- dbGetQuery(con, "SELECT * FROM students")
print(result)

🔍 Explanation:

• dbGetQuery() sends an SQL command and returns the result as a data frame.
• You can use full SQL syntax: WHERE, JOIN, GROUP BY, etc.

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🔄 4. Insert or Modify Records

dbExecute(con, "INSERT INTO students (Name, Age) VALUES ('Charlie', 22)")

🔍 Explanation:

• dbExecute() is used for write operations (INSERT, UPDATE, DELETE) that don’t return a result.

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🔎 5. List and Inspect Tables

dbListTables(con)       # Shows all tables
dbListFields(con, "students")   # Shows all columns

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❌ 6. Close the Database Connection

dbDisconnect(con)

🔍 Explanation:

• Always disconnect after completing database operations to free up resources.

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🌐 7. Connecting to MySQL or PostgreSQL (Example)

✅ MySQL Example with RMariaDB:

# install.packages("RMariaDB")
library(DBI)
con <- dbConnect(RMariaDB::MariaDB(),
                 user = "root",
                 password = "your_password",
                 dbname = "your_database",
                 host = "localhost")

✅ PostgreSQL Example:

# install.packages("RPostgres")
library(DBI)
con <- dbConnect(RPostgres::Postgres(),
                 dbname = "your_db",
                 host = "localhost",
                 port = 5432,
                 user = "postgres",
                 password = "your_pass")

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🧠 Security Tips

Tip	Description
Avoid hardcoding credentials	Use readline() or .Renviron for secrets
Use environment variables	Store credentials in .Renviron file
Disconnect when done	Prevents connection leaks

Sys.getenv("DB_PASS")

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📌 Summary – Recap & Next Steps

R supports robust integration with SQL databases. With just a few lines, you can query, transform, and load structured data into your analytics workflows.

🔍 Key Takeaways:

• Use DBI as a unified interface for various DBMS
• SQLite is easiest for local storage
• dbConnect(), dbWriteTable(), and dbGetQuery() are key functions
• Use RMariaDB or RPostgres for server databases
• Secure connections by hiding passwords and disconnecting properly

⚙️ Real-World Relevance:
Used in enterprise systems for dashboarding, ETL processes, production-grade analytics, and combining live DB records with statistical models in R.

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❓ FAQs – Database Access in R

❓ What is the best way to store credentials securely in R?
✅ Use .Renviron to load environment variables:

Sys.getenv("DB_USER")

❓ Can I run JOIN queries in dbGetQuery()?
✅ Absolutely! Use full SQL syntax:

dbGetQuery(con, "SELECT * FROM table1 JOIN table2 ON ...")

❓ What’s the difference between dbExecute() and dbGetQuery()?
✅ dbExecute() is for writing data; dbGetQuery() retrieves it.

❓ Can I use R to create and manage SQL tables?
✅ Yes. You can use dbExecute() to run any valid SQL command, including CREATE, DROP, ALTER.

❓ How do I know which database driver to use?
✅ Use:

• RSQLite for local .sqlite files
• RMariaDB for MySQL or MariaDB
• RPostgres for PostgreSQL

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