Golang/SQL - Fixing the error - Converting NULL to string is unsupported error
Converting NULL to string is unsupported errorThe 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.
1package demo
2
3type User struct {
4 Id string
5 FirstName string
6 LastName string
7}
8
9func findUserByEmail(ctx context.Context, email string) {
10 user := &User{}
11 row := DbConn.QueryRowContext(ctx, `
12 SELECT id, COALESCE(first_name, '') as first_name, COALESCE(last_name, '') as last_name
13 FROM users
14 WHERE email = $1
15 `, email)
16 err := row.Scan(&user.Id, &user.FirstName, &user.LastName)
17
18 // ...
19}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.