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Should I use select transactions?
2 Answers. In a highly concurrent application it could (theoretically) happen that data you’ve read in the first select is modified before the other selects are executed. If that is a situation that could occur in your application you should use a transaction to wrap your selects.
What does the for update do on a select statement when a transaction has been started?
The SELECT FOR UPDATE statement is used to order transactions by controlling concurrent access to one or more rows of a table. These other transactions are effectively put into a queue based on when they tried to read the value of the locked rows. …
What is the use of begin transaction in SQL Server?
BEGIN TRANSACTION represents a point at which the data referenced by a connection is logically and physically consistent. If errors are encountered, all data modifications made after the BEGIN TRANSACTION can be rolled back to return the data to this known state of consistency.
Why SELECT for UPDATE is bad?
Answer: The select for update has many issues, and select for update is especially dangerous when a transaction aborts and a “zombie” process continues to hold rows locks. The select for update is not a good locking strategy because there are many things that can go wrong.
Does SELECT lock table mysql?
SELECTs do not normally do any locking that you care about on InnoDB tables. The default transaction isolation level means that selects don’t lock stuff. A SELECT in SQL Server will place a shared lock on a table row – and a second SELECT would also require a shared lock, and those are compatible with one another.
Can we use transaction in SQL function?
1 Answer. That’s why transactions are unnecessary for sql-server functions. However, you can change transaction isolation level, for example, you may use NOLOCK hint to reach “read uncommitted” transaction isolation level and read uncommitted data from other transactions.
Is every SQL query a transaction?
6 Answers. It does nothing. All individual SQL Statements, (with rare exceptions like Bulk Inserts with No Log, or Truncate Table) are automaticaly “In a Transaction” whether you explicitly say so or not.. (even if they insert, update, or delete millions of rows).
Should I use transaction MySQL?
Transactions should be used when there is the possibility that either failure to complete or someone else reading or writing in the middle of your task could cause damage to the data.