Prepared Statements

In this lesson, explore prepared statements through one small Go program, and connect its output to the language rules behind it.

db.PrepareContext creates a statement handle that can be reused with different arguments. Parameterization separates values from SQL syntax and prevents common SQL injection patterns when used correctly.

A prepared statement consumes resources; close it when its owning scope ends. Some drivers may prepare per connection and reuse semantics vary.

Follow this diagram before executing the example. Check where a value or decision changes what runs next.

Real prepared statement pattern

stmt, err := db.PrepareContext(ctx, "UPDATE tasks SET title = ? WHERE id = ?")
if err != nil { return err }
defer stmt.Close()
_, err = stmt.ExecContext(ctx, "Study Go", 7)
if err != nil { return err }

Requires a configured db, ctx, and a driver accepting ? placeholders. See Using prepared statements.

This example is a complete program. Save it as main.go or paste it into the Go Playground.

Go code

package main

import (
	"database/sql"
	"fmt"
)

func main() {
	arg := sql.Named("owner", "Maya")
	fmt.Println("Parameter:", arg.Name, "Value:", arg.Value)
}

Output

Parameter: owner Value: Maya

sql.Named constructs one named argument. A real prepared statement uses driver-compatible placeholder names and passes its parameters at ExecContext or QueryContext time.

• Parameterized values cannot stand in for arbitrary table or column identifiers.
• Prepared statements are not automatically faster for every workload.

Write a prepared UPDATE task title statement and defer Close, checking both preparation and execution errors.

Tip: Edit the example above, predict the output, and run the modified code to test your reasoning.

You have practiced Prepared Statements in a small, self-contained program. The important habit is to predict what runs, inspect the actual output and distinguish the language rule from the particular example.

Before continuing, make sure you can explain the program to someone who has not seen it, including the line that changes its result.