Go Sql Driver Connection

In this tutorial, you'll learn about Go SQL Driver: Unknown Driver. We cover key concepts, practical examples, and best practices.

SQL driver registration -- Register SQL database drivers by importing them with a blank identifier.

The Problem

sql.Open("driver", dsn) fails with "unknown driver" if the driver package is not imported. SQL drivers register themselves via init().

Wrong

db, err := sql.Open("postgres", dsn)

Output:

$ go run main.go
panic: unknown driver "postgres"

Right

import (
    "database/sql"
    _ "github.com/lib/pq"
)
func main() {
    db, err := sql.Open("postgres",
        "host=localhost user=admin dbname=mydb sslmode=disable")
    if err != nil { log.Fatal(err) }
    defer db.Close()
}

Output:

// No error, driver registered successfully

Prevention

• Import driver with _ "github.com/lib/pq"
• Common drivers: lib/pq, go-sql-driver/mysql, mattn/go-sqlite3
• sql.Open does not actually connect
• Use db.Ping() to verify the connection
• sql.DB is safe for concurrent use

Common Mistakes with sql driver connection

1. Using head and tail instead of pattern matching, causing runtime errors on empty lists
2. Forgetting that lazy evaluation defers computation until the value is forced, causing space leaks with unevaluated thunks
3. Using return to exit a function early instead of wrapping a pure value in the monad

These mistakes appear frequently in real-world GO code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ

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