Scanning SQL rows to structures in Go can be achieved in a variety of ways. 1. Use sql.Rows.Scan to manually map fields. Make sure that the field order is consistent with the query column and pass pointers; 2. For empty columns, use the sql.NullXXX type provided by database/sql and check the .Valid attribute; 3. Consider using jmoiron/sqlx and other libraries to automatically map fields to reduce redundant code and improve maintenance. Each method is suitable for different scenarios, manual mapping is suitable for simple structures, and library assistance is suitable for complex models.
In Go, scanning SQL rows into a struct is a common task when working with databases. The key idea is to map each column in the result set to a corresponding field in your struct. If you're not using an ORM like GORM, you'll typically use the database/sql package along with the Scan method to achieve this.
Use sql.Rows.Scan with explicit field mapping
The most straightforward way to get data from a SQL row into a struct is by manually assigning each column to a struct field using rows.Scan . This approach gives you full control and works well for small structs or simple queries.
For example:
type User struct {
ID int
Name string
Age int
}
var user User
err := db.QueryRow("SELECT id, name, age FROM users WHERE id = ?", 1).Scan(&user.ID, &user.Name, &user.Age)- Make sure to pass points (
&) toScan - Field types must match the database schema
- Column order in the query must match the order of arguments passed to
Scan
This method is simple but can become tedious if you have many fields or need to do it often.
Handle nullable columns with appropriate Go types
If your table has nullable columns, you can't just use regular types like string or int — they don't support null values. Instead, use the types provided in the database/sql package such as:
-
sql.NullString -
sql.NullInt64 -
sql.NullFloat64 -
sql.NullBool
For example:
type User struct {
ID int
Name string
Nickname sql.NullString
}Then scan accordingly:
var user User
err := db.QueryRow("SELECT id, name, nickname FROM users WHERE id = ?", 1).Scan(&user.ID, &user.Name, &user.Nickname)
if err == nil && user.Nickname.Valid {
fmt.Println("Nickname:", user.Nickname.String)
}- Check
.Validbefore accessing.Stringor other value fields - This avoids runtime errors caused by trying to read NULL values ??into non-pointer types
Consider using reflectx or helper libraries for dynamic mapping
If you find yourself writing repetitive code to scan rows into structs, especially when dealing with many different models, consider using a library that automates this process.
Libraries like jmoiron/sqlx extend the standard database/sql package and allow you to scan directly into structs without having to list all fields manually:
import "github.com/jmoiron/sqlx" var user User err := db.Get(&user, "SELECT id, name, age FROM users WHERE id = ?", 1)
- No need to specify every field in
Scan - Struct field names are matched to column names (case-insensitive)
- You can use
dbx.StructScan,dbx.SliceScan, etc., depending on your needs
This makes your code cleaner and less error-prone, especially when dealing with larger structs.
Depending on your project size and complexity, you can choose between manual scanning for simplicity or structured helpers for maintainability. Either way, understanding how Scan works under the hood will help you debug issues faster and write more efficient database code in Go.
Basically that's it.
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