go data_error ai_generated true

sql: Scan error on column index 3: converting NULL to string is unsupported

ID: go/database-scan-null-field

Also available as: JSON · Markdown · 中文
90%Fix Rate
88%Confidence
1Evidence
2023-03-10First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
Go 1.18 active — — —
Go 1.19 active — — —
Go 1.20 active — — —
Go 1.21 active — — —
Go 1.22 active — — —

Root Cause

Scanning a NULL database value into a non-pointer Go type (e.g., string instead of *string or sql.NullString).

generic

中文

将数据库中的 NULL 值扫描到非指针的 Go 类型（例如，使用 string 而不是 *string 或 sql.NullString）。

Official Documentation

https://pkg.go.dev/database/sql#NullString

Workarounds

  1. 95% success Use sql.NullString or *string for nullable columns, then check .Valid before use 
    Use sql.NullString or *string for nullable columns, then check .Valid before use
  2. 90% success Define custom struct fields as pointers to handle NULLs 
    Define custom struct fields as pointers to handle NULLs

中文步骤

  1. 对可空列使用 sql.NullString 或 *string，并在使用前检查 .Valid
  2. 将自定义结构体字段定义为指针以处理 NULL

Dead Ends

Common approaches that don't work:

  1. 60% fail

    This masks the data issue and can lead to incorrect business logic if NULL has semantic meaning.

  2. 80% fail

    Pollutes the data and may break other queries or reports.