什么是更快？
合并声明
- MERGE INTO table_name
- USING dual
- ON (row_id = 'some_id')
- WHEN MATCHED THEN
- UPDATE SET col_name = 'some_val'
- WHEN NOT MATCHED THEN
- INSERT (row_id,col_name)
- VALUES ('some_id','some_val')
要么
查询select语句,然后使用update或insert语句.
- SELECT * FROM table_name where row_id = 'some_id'
如果rowCount == 0
- INSERT INTO table_name (row_id,col_name) VALUES ('some_id','some_val')
其他
- UPDATE table_name SET col_name='some_val' WHERE row_id='some_id'
解决方法
经验法则是,如果您可以在一个sql中执行此操作,则通常会在多个sql语句中执行更好.
如果这样做,我会和MERGE一起去.
另外 – 另一个建议：你可以避免在你的声明中重复数据,例如：
- MERGE INTO table
- USING (SELECT 'some_id' AS newid,'some_val' AS newval
- FROM dual)
- ON (rowid = newid)
- WHEN MATCHED THEN
- UPDATE SET colname = newval
- WHEN NOT MATCHED THEN
- INSERT (rowid,colname)
- VALUES (newid,newval)
