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SQL Correlated Subqueries Increase the Power of SQL

A SQL correlated subquery is a query which is executed one time for each record returned by the outer query. It is called _correlated_ as it is a correlation between the number of times the subquery is executed with the number of records returned by the outer query (not the subquery).

SQL Window Functions

This lesson introduces you to SQL _**window functions**_. They are a powerful kind of function, that computes a result based on a set of rows, instead of computing based on a single row. They are similar to aggregate functions. The term _window_ refers to the set of rows used to calculate the result of the function. This lesson focuses on how window functions work and the syntax to use.

SQL Window Function Examples

This lesson presents SQL window function examples. SQL Window functions are powerful functions that compute their result based on a set of rows (the `window`), instead of computing based on a single row. They are similar to [SQL aggregate functions](/sql-tutorial/intermediate-sql/sql-aggregate-functions).

Selecting Data From Multiple Tables: SQL JOINS

This lesson covers perhaps the most important element of the SQL language: the `SQL JOIN` operation. As you know, a database stores data in several tables. When you need to combine data from multiple tables you do a JOIN between the tables where the data is stored.

Visual Representation of SQL JOINS

The examples in this lesson show several `SQL JOIN` operations and Venn diagrams to show the result sets of records expected for each `JOIN` type. A non-equality `JOIN` expression is also shown.

Query Optimization

This lesson describes the query execution process and presents the most frequently used techniques to optimize query performance.

An SQL index is an independently stored data structure that belongs to a table. A table can have zero or more indexes. When used appropriately, an SQL index can speed up your query. SQL indexes are primarily used with `WHERE, JOIN` or [ORDER BY](/sql-tutorial/basic-sql/sql-order-by-limit-clauses/) clauses to optimize the access of few records. Indexes are not typically used in analytical environments where queries access big portions of the involved tables.

SQL Correlated Subqueries Increase the Power of SQL

A SQL correlated subquery is a query which is executed one time for each record returned by the outer query. It is called _correlated_ as it is a correlation between the number of times the subquery is executed with the number of records returned by the outer query (not the subquery).

SQL Window Functions

This lesson introduces you to SQL _**window functions**_. They are a powerful kind of function, that computes a result based on a set of rows, instead of computing based on a single row. They are similar to aggregate functions. The term _window_ refers to the set of rows used to calculate the result of the function. This lesson focuses on how window functions work and the syntax to use.

SQL Window Function Examples

This lesson presents SQL window function examples. SQL Window functions are powerful functions that compute their result based on a set of rows (the `window`), instead of computing based on a single row. They are similar to [SQL aggregate functions](/sql-tutorial/intermediate-sql/sql-aggregate-functions).

Selecting Data From Multiple Tables: SQL JOINS

This lesson covers perhaps the most important element of the SQL language: the `SQL JOIN` operation. As you know, a database stores data in several tables. When you need to combine data from multiple tables you do a JOIN between the tables where the data is stored.

Visual Representation of SQL JOINS

The examples in this lesson show several `SQL JOIN` operations and Venn diagrams to show the result sets of records expected for each `JOIN` type. A non-equality `JOIN` expression is also shown.

Query Optimization

This lesson describes the query execution process and presents the most frequently used techniques to optimize query performance.

An SQL index is an independently stored data structure that belongs to a table. A table can have zero or more indexes. When used appropriately, an SQL index can speed up your query. SQL indexes are primarily used with `WHERE, JOIN` or [ORDER BY](/sql-tutorial/basic-sql/sql-order-by-limit-clauses/) clauses to optimize the access of few records. Indexes are not typically used in analytical environments where queries access big portions of the involved tables.

SQL Correlated Subqueries Increase the Power of SQL

A SQL correlated subquery is a query which is executed one time for each record returned by the outer query. It is called _correlated_ as it is a correlation between the number of times the subquery is executed with the number of records returned by the outer query (not the subquery).

SQL Window Functions

This lesson introduces you to SQL _**window functions**_. They are a powerful kind of function, that computes a result based on a set of rows, instead of computing based on a single row. They are similar to aggregate functions. The term _window_ refers to the set of rows used to calculate the result of the function. This lesson focuses on how window functions work and the syntax to use.

SQL Window Function Examples

This lesson presents SQL window function examples. SQL Window functions are powerful functions that compute their result based on a set of rows (the `window`), instead of computing based on a single row. They are similar to [SQL aggregate functions](/sql-tutorial/intermediate-sql/sql-aggregate-functions).

Selecting Data From Multiple Tables: SQL JOINS

This lesson covers perhaps the most important element of the SQL language: the `SQL JOIN` operation. As you know, a database stores data in several tables. When you need to combine data from multiple tables you do a JOIN between the tables where the data is stored.

Visual Representation of SQL JOINS

The examples in this lesson show several `SQL JOIN` operations and Venn diagrams to show the result sets of records expected for each `JOIN` type. A non-equality `JOIN` expression is also shown.

Query Optimization

This lesson describes the query execution process and presents the most frequently used techniques to optimize query performance.

An SQL index is an independently stored data structure that belongs to a table. A table can have zero or more indexes. When used appropriately, an SQL index can speed up your query. SQL indexes are primarily used with `WHERE, JOIN` or [ORDER BY](/sql-tutorial/basic-sql/sql-order-by-limit-clauses/) clauses to optimize the access of few records. Indexes are not typically used in analytical environments where queries access big portions of the involved tables.

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