Converting NULL to string is unsupported error
The error above is thrown whenever a Go program tries to scan a query result that contains at least one column whose value is NULL to a struct defined with primitive types instead of sql.NullString type.
To solve this issue at the query level, the SQL function COALESCE comes in handy.
package demo
type User struct {
Id string
FirstName string
LastName string
}
func findUserByEmail(ctx context.Context, email string) {
user := &User{}
row := DbConn.QueryRowContext(ctx, `
SELECT id, COALESCE(first_name, '') as first_name, COALESCE(last_name, '') as last_name
FROM users
WHERE email = $1
`, email)
err := row.Scan(&user.Id, &user.FirstName, &user.LastName)
// ...
}
When the query above is executed, the function COALESCE will replace the NULL value of the columns first_name and last_name returned by the database for the value passed as second argument, which is an empty string.