删除数据库中特定字段相同但特定列值为空的行

要删除数据库中特定字段相同但特定列值为空的行，可以使用SQL的DELETE语句结合适当的条件。以下是几种常见数据库系统的解决方案：

MySQL/MariaDB

DELETE t1 FROM table_name t1
INNER JOIN table_name t2 
WHERE t1.common_field = t2.common_field 
AND t1.target_field IS NULL 
AND t2.target_field IS NOT NULL;

PostgreSQL

DELETE FROM table_name t1
USING table_name t2
WHERE t1.common_field = t2.common_field 
AND t1.target_field IS NULL 
AND t2.target_field IS NOT NULL;

SQL Server

DELETE t1
FROM table_name t1
INNER JOIN table_name t2 ON t1.common_field = t2.common_field
WHERE t1.target_field IS NULL 
AND t2.target_field IS NOT NULL;

Oracle

DELETE FROM table_name t1
WHERE t1.target_field IS NULL
AND EXISTS (
    SELECT 1 FROM table_name t2
    WHERE t2.common_field = t1.common_field
    AND t2.target_field IS NOT NULL
);

SQLite

DELETE FROM table_name
WHERE target_field IS NULL
AND common_field IN (
    SELECT common_field 
    FROM table_name
    WHERE target_field IS NOT NULL
);

注意事项

1. 在执行删除操作前，建议先运行SELECT语句验证将要删除的记录：

   SELECT * FROM table_name t1
   INNER JOIN table_name t2 ON t1.common_field = t2.common_field
   WHERE t1.target_field IS NULL AND t2.target_field IS NOT NULL;
   

2. 对于大型表，考虑分批删除以避免锁表时间过长。

3. 在执行删除操作前备份数据库。

4. 如果只需要保留一条非空记录，可以使用更复杂的逻辑，例如：

   DELETE FROM table_name
   WHERE target_field IS NULL
   AND common_field IN (
      SELECT common_field 
      FROM table_name
      GROUP BY common_field
      HAVING COUNT(*) > 1
   );
   

您需要根据具体的数据库类型和表结构调整上述SQL语句。