Probably the most common way to join tables in SQL is with the ON clause. But that’s not the only way.
We can also join with the USING clause, which can be more concise, while providing the same or similar results. And there’s also the concept of a natural join, which is more concise again.
Let’s take a look at these three join options and compare them side by side.
Continue readingPerhaps 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.
SQL joins are fundamental operations in relational databases, allowing us to combine data from multiple tables. Two of the most commonly used join types are INNER JOIN and LEFT JOIN. Understanding the difference between these joins is crucial if you intend to use joins in your queries.
In this article, we’ll look at the difference between the INNER JOIN and LEFT JOIN using a simple example.
In SQL, the self join is a join technique where we join a table with itself. Other join types will join a table with another table, but the self join simply joins with itself.
Self joins can be useful when working with hierarchical or recursive data within a single table.
Continue readingWhile INNER and LEFT JOINs are the workhorses of SQL queries, T-SQL offers several more advanced join techniques that can be invaluable for complex data analysis and manipulation. This article explores some of these powerful join methods and how they can enhance our queries.
In SQL, you can join three tables or more by adding another join after the first one.
You can also run nested joins by specifying one join as the join condition for another.
Continue readingThe SET FORCEPLAN statement overrides the logic used by the SQL Server query optimizer to process a T-SQL SELECT statement.
More specifically, when FORCEPLAN is set to ON, the query optimizer processes a join in the same order as the tables appear in the FROM clause of a query.
This also forces the use of a nested loop join unless other types of joins are required to construct a plan for the query, or they are requested with join hints or query hints.
Continue readingA LEFT SEMI JOIN is kind of a half-join. It returns any distinct values that are returned by both the query on the left and right sides of the query.
However, when using T-SQL in SQL Server, if you try to explicitly use LEFT SEMI JOIN in your query, you’ll probably get the following error:
A LEFT ANTI SEMI JOIN is a type of join that returns only those distinct rows in the left rowset that have no matching row in the right rowset.
But when using T-SQL in SQL Server, if you try to explicitly use LEFT ANTI SEMI JOIN in your query, you’ll probably get the following error:
A SQL join is where you run a query that joins multiple tables.
This SQL joins tutorial presents basic examples of SQL joins, as well as an introduction to the various join types.
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