When using relational database management systems (RDBMSs) we often hear terms like DDL, DML, DQL, DCL, and TCL. But what exactly are they?
In this article we’ll look at what TCL stands for in the context of SQL, and what it does.
transactions
How to Backup the Transaction Logs in Azure SQL Edge (T-SQL)
By default, databases created in Azure SQL Edge use the simple recovery model. This means that you can’t perform log backups on these databases.
Fortunately, you can change a database’s recovery model to full recovery mode, which will enable you to back up the logs.
How to Fix “The COMMIT TRANSACTION request has no corresponding BEGIN TRANSACTION” in SQL Server
If you’re receiving error Msg 3902, Level 16, which reads “The COMMIT TRANSACTION request has no corresponding BEGIN TRANSACTION”, it’s probably because you’ve got a stray COMMIT statement.
You could be getting this due to implementing error handling, and forgetting that you’ve already committed or rolled back the transaction elsewhere in your code.
How Implicit Transactions Work in SQL Server
There are four transaction modes in SQL Server. One of these is implicit mode.
In SQL Server, an implicit transaction is when a new transaction is implicitly started when the prior transaction completes, but each transaction is explicitly completed with a COMMIT or ROLLBACK statement.
This is not to be confused with autocommit mode, where the transaction is started and ended implicitly.
SQL Transactions Tutorial
In SQL, transactions are used to maintain data integrity by ensuring that a sequence of SQL statements execute completely or not at all.
Transactions manage sequences of SQL statements that must be executed as a single unit of work, so that the database never contains the results of partial operations.
When a transaction makes multiple changes to the database, either all the changes succeed when the transaction is committed, or all the changes are undone when the transaction is rolled back.
How transaction_timestamp() Works in PostgreSQL
In PostgreSQL, the transaction_timestamp() function returns the current date and time (including the time zone offset), at the start of the current transaction.
It’s the equivalent of the traditional Postgres function now().
It’s also similar to the current_timestamp function (when called without an argument), except that it’s named to clearly reflect what it does.
The transaction_timestamp() function doesn’t accept any parameters, so you can’t specify its precision, whereas current_timestamp can be called with or without a precision parameter.
Also, transaction_timestamp() is a non-SQL-standard function.
What is OLTP?
OLTP (Online Transactional Processing) is a category of data processing that is focused on transaction-oriented tasks. OLTP typically involves inserting, updating, and/or deleting small amounts of data in a database.
OLTP mainly deals with large numbers of transactions by a large number of users.
What does ACID mean in Database Systems?
In database systems, ACID (Atomicity, Consistency, Isolation, Durability) refers to a standard set of properties that guarantee database transactions are processed reliably.
ACID is especially concerned with how a database recovers from any failure that might occur while processing a transaction.
An ACID-compliant DBMS ensures that the data in the database remains accurate and consistent despite any such failures.