使用SQLAlchemy查询数据库,仅返回对象 mystock是对象,其中包含您需要的信息。 对于从mystock对象访问特定列,可以这样做 mystock.stock_name 它将返回所选行的stock_name列的值。 你可以进一步阅读这些文件 Flask SQLAlchemy Query仅第一次工作 正如我在注释中提到的,查询的字符串包含额外的空间。我将按如下方式修复...
将当前的事务回滚到保存点savepoint1。 obclient>ROLLBACKTOSAVEPOINTsavepoint1;Query OK,0rowsaffected
# User@Host:root[root]@ localhost[]# Query_time:10.234Lock_time:8.567Rows_sent:1Rows_examined:10000UPDATEordersSETstatus='shipped'WHEREorder_id=12345; 从这个记录可以看出,这个更新订单状态的SQL语句执行时间长达10.234秒,其中锁等待时间就占了8.567秒,而且扫描了10000行数据。这就提示我们这个SQL语句可能存...
transaction. After you create a table, the following statements start a named transaction, insert two rows, and then roll back the transaction named in the variable@TransactionName. Another statement outside of the named transaction inserts two rows. The query returns the results of the previous ...
query — they cannot start or commit that transaction, since there would be no context for them to execute in. However, a block containing an EXCEPTION clause effectively forms a subtransaction that can be rolled back without affecting the outer transaction. ...
表から過去のデータを取り出す方法の詳細は、「SELECT」の「flashback_query_clause」を参照してください。 FLASHBACK TABLE文を使用する方法の詳細は、『Oracle Databaseバックアップおよびリカバリ・ユーザーズ・ガイド』を参照してください。 前提...
Write a SQL query to create a savepoint after inserting data into a table and rollback to that savepoint if an error occurs later in the transaction. Write a SQL query to use savepoints to undo specific steps in a multi-step transaction without affecting the entire operation. ...
Write a SQL query to rollback a transaction if an error occurs during execution.Solution:BEGIN TRANSACTION; -- Begin the transaction. -- Attempt to insert data into the Employees table. INSERT INTO Employees (EmployeeID, Name, Age, Salary) VALUES (2, 'Bob Smith', 25, 45000); --...
SQL> SELECT 174 * 8 || 'KB' FROM dual; 174*8| --- 1392KB 五、计算UNDO表空间的大小 计算公式: MAX(undoblks)/600 * MAX(maxquerylen) 位于v$undostat * db_block_size 位于v$parameter --创建演示环境 SQL> INSERT INTO tb_test SELECT employee_id,first_name FROM hr.employees; 107 ...
MAX(undoblks)/600 * MAX(maxquerylen) 位于v$undostat * db_block_size 位于v$parameter--创建演示环境 SQL> INSERT INTO tb_test SELECT employee_id,first_name FROM hr.employees; 107 rows created SQL> INSERT INTO tb_test SELECT * from tb_test; ...