go data_error ai_generated true

sql: Scan error on column index 2: converting NULL to string is unsupported

ID: go/database-sql-null-value

Also available as: JSON · Markdown · 中文
80%Fix Rate
90%Confidence
0Evidence
2024-02-14First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1.18 active — — —
1.19 active — — —

Root Cause

Scanning a NULL database column into a non-nullable Go type (e.g., string) without using sql.NullString.

generic

中文

将数据库中的NULL列扫描到不可为空的Go类型（如string）中，而未使用sql.NullString。

Workarounds

  1. 95% success 
    var s sql.NullString
if err := rows.Scan(&s); err != nil {
    // handle error
}
if s.Valid {
    fmt.Println(s.String)
}
  2. 80% success 
    Use COALESCE in SQL query to convert NULL to default value.

Dead Ends

Common approaches that don't work:

  1. 70% fail

    NULL is not the same as an empty string and can lead to data loss.

  2. 90% fail

    Go does not allow direct casting of NULL to string.