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to ensure acid performance, but this will be relatively low and the database system can be said to be basically unusable. Therefore, in order to improve concurrency, we need to reduce the requirement of isolation. Depending on your business needs, we need to trade off between the concurrency and isolation levels, and a common DBMS will typically provide multiple isolation levels for users to choose from.Ii. Abnormal Phenomena 2.1 dirty write (Dirty Write)There are two transactions

Delete multiple table data in MySQLDelete deletes multiple table data, how can you delete data from multiple associated tables at the same time? Here's an in-depth explanation:1. Delete from T1 where condition2. Delete t1 from T1 where condition3. Delete T1 from T1,t2 where

Delete bitsCN.com from another table Delete another table based on the table DELETE: how can I DELETE data from multiple associated tables at the same time? Here is an in-depth explanation: 1. delete from t1 where condition 2. delete t1 from t1 where condition 3. delete t1 from

We have talked a lot about how to delete multi-table data in MySQL. The following is an in-depth analysis and discussion on how to delete multi-table data in MySQL, I hope you will learn how to delete multi-table data in MySQL. 1. delete from t1 where Condition 2. delete t1 from t1 where Condition 3. delete t1 from

Oracle automatically clears logs in the materialized view. Oracle determines when to delete the materialized view log based on the registration information on the base table of the Materialized View and the refresh of the materialized view. The registration information of the materialized view is cleared when the materialized view is deleted. However, when the materialized view is created in a remote database, the deletion of registration information may be more complex. If the materialized vie

Student score Table (Stuscore):Name: Name course: Subject Score: Score No.: StuidZhang San Mathematics 89 1Zhang San Languages 80 1Zhang San English 70 1John Doe Mathematics 90 2John Doe Languages 70 2John Doe English 80 21. Calculate the total number of each person and rank (requires display field: Name, overall scores)Answer: Select Name,sum (Score) as Allscore from Stuscore Group by name ORDER by Allscore2. Calculate each person's total and rank (required field: number, name, overall)Answer:

(); (1) /* (2 )*/ Try { Thread. sleep (3000 ); } Catch (InterruptedException e ){ System. out. println ("Interrupted "); } } } } Public class TestThread { Public static void main (String [] args ){ TestThreadMethod t1 = new TestThreadMethod ("t1 "); TestThreadMethod t2 = new TestThreadMethod ("t2 "); T1.setPriority (Thread. MAX_PRIORITY ); T2.setPriority (Threa

article, we solved the deadlock problem in that scenario. This time, let's analyze why the deadlock occurs? Let's review the two SP statements:Create proc P1 @ P1 intSelect C2, C3 from T1 where C2 between @ P1 and @ P1 + 1GoCreate proc P2 @ P1 intUpdate T1 set C2 = C2 + 1 where c1 = @ p1Update T1 set C2 = c2-1 where c1 = @ p1Go Strange! P1 has no insert, no Dele

Comparison between four methods for batch ORACLE update and four methods for oracle update Software Environment Windows 2000 + ORACLE9i Hardware environment CPU 1.8G + RAM 512 M Now we have two tables: T1 -- large table 10000 T1_FK_ID T2 -- small table 5000 T2_PK_ID T1 is associated with the primary key ID of T2. The simulation data is as follows: -- T2 contains 5000 pieces of data Create table T2 As Selec

One, function From the beginning of contact with JS feel good flexible, everyone's writing is different, such as a function on the N-type such as: function ShowMsg () {},var showmsg=function () {},showmsg=function () {} There seems to be no difference, is the same, really the same, we look at the following example Copy Code code as follows: ///----------------------------------------------------------------------------------------- ------- function definition: named funct

) Other transactions cannot read table, update and deleteCross-read transactions use row versioning.Use snapshot Isolation.Use a bound connection.-----------------------------Analyze and resolve SQL Server deadlock issues (cont.)Above, we solved the deadlock problem for that scene. This time, let's analyze why we have a deadlock. Look again at the two SP notation:CREATE PROC p1 @p1 int asSELECT C2, C3 from T1 WHERE C2 between @p1 and @p1 +1GOCREATE PR