Sql update in select subquery

In queries that include a correlated subquery also known as a repeating subquery , the subquery depends on the outer query for its values. This means that the subquery is executed repeatedly, once for each row that might be selected by the outer query. This query retrieves one instance of each employee's first and last name for which the bonus in the SalesPerson table is and for which the employee identification numbers match in the Employee and SalesPerson tables.

The previous subquery in this statement cannot be evaluated independently of the outer query. It needs a value for Employee. That is exactly how this query is evaluated: SQL Server considers each row of the Employee table for inclusion in the results by substituting the value in each row into the inner query. These two query samples represent a decomposition of the previous sample with the correlated subquery. The result is 0. Because this is false, the row for Syed Abbas is not included in the results of the previous sample query with the correlated subquery.

Go through the same procedure with the row for Pamela Ansman-Wolfe. Correlated subqueries can also include table-valued functions in the FROM clause by referencing columns from a table in the outer query as an argument of the table-valued function. In this case, for each row of the outer query, the table-valued function is evaluated according to the subquery. Many statements in which the subquery and the outer query refer to the same table can be stated as self-joins joining a table to itself.

For example, you can find addresses of employees from a particular state using a subquery:. Table aliases e1 and e2 are required because the table being joined to itself appears in two different roles.

Aliases can also be used in nested queries that refer to the same table in an inner and outer query. Explicit table aliases make it clear that a reference to Person. Address in the subquery does not mean the same thing as the reference in the outer query. After the subquery returns results, the outer query makes use of them. The following query finds the names of all the wheel products that Adventure Works Cycles makes. This statement is evaluated in two steps.

First, the inner query returns the subcategory identification number that matches the name 'Wheel' Second, this value is substituted into the outer query, which finds the product names that go with the subcategory identification numbers in Production. One difference in using a join rather than a subquery for this and similar problems is that the join lets you show columns from more than one table in the result. For example, if you want to include the name of the product subcategory in the result, you must use a join version.

The following query finds the name of all vendors whose credit rating is good, from whom Adventure Works Cycles orders at least 20 items, and whose average lead time to deliver is less than 16 days. As we can see, the PersonCityName column data of the Persons table have been updated with the City column data of the AddressList table for the matched records for the PersonId column.

Regarding this method, we should underline the following significant points. If the subquery finds more than one matched row, the update query will return an error, as shown below:. In this article, we learned to update the data in a table with the data where they are contained in other tables. PersonId INT. PersonName , PersonLastName. N 'Salvador' , N 'Williams' ,. N 'Lawrence' , N 'Brown' ,.

N 'Gilbert' , N 'Jones' ,. N 'Ernest' , N 'Smith' ,. N 'Jorge' , N 'Johnson'. PersonId , PostCode , City. City ,. AddressList Addr. ON Per. ON Addr.

PostCode ,. Name Then note that we have two table aliases a and b. RedBassett 3, 3 3 gold badges 29 29 silver badges 47 47 bronze badges. Thank you for this answer! To help others reading this, can you quickly add an explanation as to why this code solves the problem? Here's an example of that: update [dbName]. ID and mt2. Graham Laight Graham Laight 4, 3 3 gold badges 28 28 silver badges 26 26 bronze badges. So then you are simply counting the entire table. I stand by my down vote, this has nothing to do with the question regardless of the title — crthompson.

That's your prerogative, but the title of this thread is "update query using subquery", and my example self-evidently does exactly that. Hence for the given example, the most reliable query is like the following. Name ;. Memin Memin 2, 22 22 silver badges 25 25 bronze badges. Sign up or log in Sign up using Google. By comparing this quantity to 10, we can determine whether a given wine should be eliminated.

Subqueries are like building blocks in SQL. If you want to learn more about subqueries, I suggest the article Subquery vs. Back to articles list Articles Cookbook. Tags: sql learn sql subquery. A correlated subquery is a subquery that is executed many times—once for each record row returned by the outer main query. Sounds complex? Learn how to use a nested query in SQL. SQL Subqueries. The article describes what a subquery is and what these useful statements look like.

Correlated subqueries are the only way to solve some SQL statements.