SQL SELECT TOP 子句 SQL Server / MS Access 语法: SELECTTOP number|percentcolumn_name(s) FROMtable_name WHEREcondition; MySQL 语法: SELECTcolumn_name(s) FROMtable_name WHEREcondition LIMIT number; Oracle 12 语法: SELECTcolumn_name(s) FROMtable_name ORDERBYcolumn_name(s) FETCHFIRSTnumberROWSONL...
如果SQL 在執行 DELETE 陳述式時發現錯誤,則會停止刪除資料並傳回負 SQLCODE。 如果您指定 COMMIT (*ALL)、COMMIT (*CS)、COMMIT (*CHG) 或 COMMIT (*RR) ,則不會刪除表格中的任何橫列 (此陳述式已刪除的橫列 (如果有的話) 會還原為先前的值)。 如果指定 COMMIT (*NONE) ,任何已刪除的橫列 不會 還...
我们可以采取以下步骤: -- 开始一个事务BEGINTRANSACTION;-- 假设执行了误删除操作DELETEFROMemployeesWHEREid=1;-- 查看日志中的操作记录SELECT*FROMfn_dblog(NULL,NULL)WHEREOperation='LOP_DELETE_ROWS';-- 如果确认要撤销,则可以进行回滚ROLLBACKTRANSACTION; 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. ...
UPDATE pay_stream a LEFT JOIN pay_main b ON a.pay_id = b.pay_id AND b.pay_time >= '2017-08-12 00:00:00' SET a.return_amount = 0 WHERE b.pay_id IS NULL; id select_type table partitions type possible_keys key key_len ref rows filtered Extra --- --- --- --- --- -...
-- 使用系统函数和视图查看已删除的数据SELECT[CurrentLSN],[TransactionID],[BeginTime],[EndTime],[TransactionName],[TransactionSID]FROMsys.fn_dblog(NULL,NULL)WHERE[Operation]='LOP_DELETE_ROWS'AND[AllocUnitName]='dbo.TestTable' 1. 2.
删除后的SQL执行情况 #删除50w数据 mysql> delete from user limit 500000; Query OK, 500000 rows affected (3.70 sec) #分析表统计信息 mysql> analyze table user; +---+---+---+---+ | Table | Op | Msg_type | Msg_text | +---+---+---+---+ | test.user | analyze | status | ...
2.1 删除SQL加锁分析 根据非唯一索引删除一条存在记录 delete from t where c1=5; Query OK, 1 rows affected (0.00 sec) ---TRANSACTION 146749, ACTIVE 9 sec 4 lock struct(s), heap size 1184, 3 row lock(s), undo log entries 1 MySQL thread id 1, OS thread handle 0x7f61ab1c7700, quer...
No rows are deleted if value1 is greater than or equal to value2, or if value1 or value2 is the null value. For the period condition that is specified with FROM value1 TO value2, the period that is specified by period-name in a row of the target table of the delete: Overlaps ...
内部不会真正删除空间,而且做标记删除,即将delflag:N修改为delflag:Y,commit之后会会被purge进入删除链表,如果下一次insert更大的记录,delete之后的空间不会被重用,如果插入的记录小于等于...+---+---+ 4 rows in set (0.00 sec) 删除后的SQL执行情况 #删除50w数据 mysql> delete from...50W 10.499000 7868...
拿到报错的参数,查询要删除的数据也不多,联系dba同学确认没有死锁日志,但出现大量慢sql,那为什么这条sql会是慢sql呢? 问题复现 表结构简化如下:CREATE TABLE `t_table_1` ( `id` bigint(20) NOT NULL AUTO_INCREMENT, `task_id` bigint(20) NOT NULL, PRIMARY KEY (`id`), KEY `idx_task_id` (`...