The HANDLER statement in MySQL provides a low-level mechanism to directly access storage engine-level functionality, bypassing some of the overhead associated with regular SQL queries. It can be especially useful for traversing a database in high-performance scenarios.
HANDLER is available for MyISAM and InnoDB tables, and can be used as a faster alternative to the SELECT statement.
The MERGE statement in SQL Server allows us to perform INSERT, UPDATE, and DELETE operations in a single query. This makes it an efficient way to synchronize two tables, typically between a source and a target, based on a defined condition. Rather than running separate queries to handle insertions, updates, and deletions, we can combine all of these operations into one statement; the MERGE statement.
Perhaps one of the lesser-known clauses when it comes to SQL joins is the USING clause. While the more widely-used ON clause allows us to explicitly specify join conditions, the USING clause simplifies the syntax when the join is based on columns with the same name in both tables.
In this article, we’ll dive into the USING clause, compare it to the ON clause, and look at examples that illustrate the difference.
Most relational database management systems support the TRUNCATE statement, and PostgreSQL is no exception.
That said, PostgreSQL has a few differences in the way its TRUNCATE statement works when compared to many other RDBMSs.
In this article, we’ll explore the various features of PostgreSQL’s implementation of the TRUNCATE statement, along with examples to demonstrate.
In SQL Server, “schema-bound” refers to a specific feature that ensures a SQL object, such as a view or function, is tightly linked to the schema of the underlying tables or other database objects it references. When a view or function is schema-bound, the underlying tables or objects cannot be altered in a way that would break the view or function’s dependencies.
Continue readingSQL Server has an OUTPUT clause that we can use any time we do an INSERT, UPDATE, DELETE, or MERGE operation. It allows us to retrieve information from modified rows during such operations. This can be especially useful for auditing, logging, or understanding the impact of database changes without needing an additional query.
Let’s look at how the OUTPUT clause can help us log the data changes in our database.
Common table expressions (CTEs) are a feature that we can use in SQL to help simplify complex queries and enhance readability. They can help with things like code readability, performance, recursive queries, and more.
This article explores what CTEs are, their syntax, types, use cases, and best practices, along with examples to help illustrate their usage.
Continue readingIn PostgreSQL, both UNIQUE indexes and UNIQUE constraints can be used to enforce uniqueness on columns.
So you may be wondering; if that’s true, why have both? And are there any circumstances that we should choose one over the other?
Let’s find out.
Continue readingStructured Query Language (SQL) is the backbone of relational database management systems (RDBMSs), enabling users to query, manipulate, and define data. One of the most fundamental concepts in SQL, and one that all SQL developers should understand, is the data type.
Whenever we create a column in SQL, we must define its data type. Similarly, when we create a variable, we define its data type.
So, why is the data type so important? Let’s find out.
Continue readingWhen using PostgreSQL’s psql command line tool, we can use the \dt command to get a list of tables. This meta-command can display all tables, or just tables that match certain patterns. Below is an overview of how \dt works, its options, and examples of its various uses.