我在MySQL incident_archive 中有一個包含數百萬筆記錄的大表，我想按created 列對行進行排序，並保留前X 行並刪除其餘行，最有效的方法是什麼。
到目前為止，我用 Python 提出了這個解決方案：
def do_delete_archive(rowsToKeep):
if rowsToKeep > 0:
db_name = find_environment_value('DB_NAME', False, "dbname")
db_host = find_environment_value('DB_HOST', False, "host")
db_user = find_environment_value('DB_USER', False, "username")
db_pass = find_environment_value('DB_PASS', False, "password")
db = MySQLdb.connect(host=db_host,user=db_user,passwd=db_pass,db=db_name)
cursor = db.cursor()
sql = f"""DELETE FROM `incident_archive`
WHERE incident_id NOT IN
( SELECT incident_id FROM
( SELECT incident_id FROM `incident_archive` ORDER BY created DESC LIMIT {rowsToKeep}) foo) LIMIT 10000;"""
try:
rowcount = rowsToKeep+ 1
while rowcount > rowsToKeep:
cursor.execute(sql)
db.commit()
rowcount = cursor.rowcount
print(f"--- Affected Rows: {rowcount} ---")
except:
db.rollback()
我在這裡遇到的問題是，如果 rowsToKeep 的值大於或等於 10000，則此方法將不起作用，此過程的更好方法是什麼？
**注意：rowsToKeep 值是動態的，這表示它可以更改。
我想出了以下解決方案：
注意：閾值是包含我們希望在範例中保留 1000 個的最大記錄數的變數
sqlCreate = f"""CREATE TABLE new_incident_archive LIKE incident_archive;""" print(f"Running query is: {sqlCreate}") cursor.execute(sqlCreate) print(f"Done with: {sqlCreate}") sqlInsert = f"""INSERT INTO new_incident_archive SELECT * FROM `incident_archive` ORDER BY created DESC LIMIT {threshold}""" print(f"Running query is: {sqlInsert}") cursor.execute(sqlInsert) db.commit() print(f"Done with: {sqlInsert}") sqlDrop = f"""DROP TABLE incident_archive""" print(f"Running query is: {sqlDrop}") cursor.execute(sqlDrop) print(f"Done with: {sqlDrop}") sqlRename = f"""RENAME TABLE `new_incident_archive` TO `incident_archive`;""" print(f"Running query is: {sqlRename}") cursor.execute(sqlRename) print(f"Done with: {sqlRename}")