A subquery is a query that returns one or more rows of data from a parent table.
An example of a common use for a subquery is to return the total amount of sales for each customer.
Subqueries are used to retrieve data from a table in SQL. They are also known as cross-joins.
There are many types of subqueries that can be used in SQL.
Example 1: With a subquery, we can retrieve data from the same table, but with different conditions.
Example 2: We can use a subquery to return all the rows that meet a certain condition.
Example 3: A subquery is useful when we need to select only one column from more than one table, but with different conditions.
Subqueries are used when you want to work with a subset of data in a SQL statement. They are typically used in SQL statements to filter, sort, and group data.
UNION ALL is a SQL Server command. It is used to combine multiple SELECT statements into a single SELECT statement. While UNION is used to combine rows from multiple tables, UNION ALL combines columns from the same table.
Subqueries are useful when you want to get the result of a query without having to use the SELECT statement. They can be used in different ways such as filtering data or grouping data by specific criteria.
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The course is very good. I have stuck at a point that how you create multiple rows with a single insert in sales.customer table. I get only one customer data. this table is related to bikestore data.
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