Web共享锁 (lock in share mode) 简介 允许不同事务之前共享加锁读取，但不允许其它事务修改或者加入排他锁 如果有修改必须等待一个事务提交完成，才可以执行，容易出现死锁 共享锁事务之间的读取 session1: start transaction; select * from test where id = 1 lock in share mode; session2: start transaction; select * from test where id = 1 lock in share mode; 此时 … WebJan 28, 2024 · Shared lock (S) is used to read data. Although a shared lock does not prevent the concurrent transactions to read the same data (placing a shared lock on the same resource), it prevents the modification of that data by the concurrent transactions. Exclusive lock (X) is requested to modify data.
LOCK IN SHARE MODE - Database Administrators Stack Exchange
WebNov 29, 2007 · *Here, we lock the table in share mode EXEC SQL LOCK TABLE GLDM IN SHARE MODE END-EXEC. EXEC SQL LOCK TABLE GLDV IN SHARE MODE END-EXEC. EXEC SQL DECLARE D_ACCOUNT_CURSOR CURSOR FOR SELECT /*+ FIRST_ROWS */ ===== Comments. Please sign in to comment. Toggle Dismiss. Locked Post. New comments … WebLOCK IN SHARE MODE, or from reading the data in certain transaction isolation levels. Consistent reads ignore any locks set on the records that exist in the read view. (Old … cookbook for couples cooking together
SQL Server, Locks object - SQL Server Microsoft Learn
Web1. La diferencia entre los bloqueos de línea y los bloqueos de la mesa. Intensidad de bloqueo: bloqueo de la mesa> Bloqueo de línea Eficiencia de bloqueo: bloqueo de la mesa> bloqueo de bloqueo Probabilidad de conflicto: bloqueo de la mesa> Bloqueo de línea Rendimiento concurrente: bloqueo de mesa Web使用SELECT ...FOR UPDATE实现. 使用 SELECT ... FOR UPDATE 语句锁定的行，在当前事务中可以被读取，但在其他事务中不能被读写。这是因为 SELECT ... FOR UPDATE 语句获得的是排他锁（Exclusive Lock），其他事务无法获取到该行的共享锁（Shared Lock），因此不能读写该行。; 示例： WebFeb 9, 2024 · Table-Level Lock Modes ACCESS SHARE (AccessShareLock) Conflicts with the ACCESS EXCLUSIVE lock mode only. The SELECT command acquires a lock of this mode on referenced tables. In general, any query that only reads a table and does not modify it will acquire this lock mode. ROW SHARE (RowShareLock) cookbook for dummies recipes