Table of Contents
- 1 What happens in MySQL when 2 users update the same row at the same time?
- 2 What happens when you use update command?
- 3 Does MySQL view update automatically?
- 4 Can we use select and update together?
- 5 What is the use of UPDATE command in SQL?
- 6 Which clause allows us to select those rows?
- 7 Do SQL views need to be refreshed?
- 8 Is there a way to update only one row in MySQL?
- 9 How do you handle concurrent updates in SQL Server?
- 10 How to update a row in a table with one server request?
What happens in MySQL when 2 users update the same row at the same time?
Although it may seem like two users are updating the same row of data at the same time, the MySQL DBMS would prevent this from happening; instead one user’s update would go first and one would go second. The result would be that both updates would go through (just not at the same time).
What happens when you use update command?
An SQL UPDATE statement changes the data of one or more records in a table. Either all the rows can be updated, or a subset may be chosen using a condition.
What will happen if two users attempt to update the same record in a database?
If two clients fetched the same version of the same data, they could unwittingly overwrite each-other’s changes if they assumed that they were the only ones editing that data at that time.
Does MySQL view update automatically?
Yes, Views automatically update in MySQL; including, but not limited to: Changing table structures. Insert/Update/Delete procedures on Tables.
Can we use select and update together?
UPDATE from SELECT: The MERGE statement The MERGE statement can be very useful for synchronizing the table from any source table. In this method, the reference table can be thought of as a source table and the target table will be the table to be updated. The following query can be an example of this usage method.
Does select for update block read?
A SELECT FOR UPDATE reads the latest available data, setting exclusive locks on each row it reads.
What is the use of UPDATE command in SQL?
The UPDATE statement is used to modify the existing records in a table.
Which clause allows us to select those rows?
|Que.||The ______ clause allows us to select only those rows in the result relation of the ____ clause that satisfy a specified predicate.|
Do views update automatically?
Yes, they are updated, every time you use them. Views are not automatically cached. When you SELECT from a view, the database has to run the query stored in the view to get the result set to use in your statement The data you ‘see’ in a view, is not actually stored anywhere, and is generated from the tables on the fly.
Do SQL views need to be refreshed?
3 Answers. Views need to be refreshed if the underlying tables change at all. That can change the datatypes of the view’s columns or rearrange its indexes. Therefore, it needs to know.
Is there a way to update only one row in MySQL?
Apparently mysql does have something that might be of use, especially if you are only updating one row. This example is from: http://lists.mysql.com/mysql/219882 UPDATE mytable SET mycolumn = @mycolumn := mycolumn + 1 WHERE mykey = ‘dante’; SELECT @mycolumn;
How to reset time to zero after SELECT query in MySQL?
So what you’re trying to do is reset timeto zero whenever you access a row — sort of like a trigger, but MySQL cannot do triggers after SELECT. Probably the best way to do it with one server request from the app is to write a stored procedure that updates and then returns the row.
How do you handle concurrent updates in SQL Server?
One way to handle this is to do it in a transaction, and make your SELECT query take an update lock on the rows selected until the transaction completes. This eliminates the possibility that a concurrent client updates the rows selected in the moment between your SELECT and your UPDATE.
How to update a row in a table with one server request?
Probably the best way to do it with one server request from the app is to write a stored procedure that updates and then returns the row. If it’s very important to have the two occur together, wrap the two statements in a transaction. Share Improve this answer