Tag: common table expressions (CTE)

Fixing Error 4121 When Using a CTE with FOR XML in SQL Server

Posted on by Ian

If you’re trying to use a common table expression (CTE) that produces XML in SQL Server, but you’re getting error 4121, which reads something like “Cannot find either column “EmployeeData” or the user-defined function or aggregate “EmployeeData.query”, or the name is ambiguous” it might be that you’re trying to query the XML in the outer query, but your CTE isn’t outputting the XML as an actual xml type.

The FOR XML result must be an xml type in order to process the result on the server.

To fix this issue, make sure the CTE outputs the result using the xml data type.

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Using the ORDER BY Clause Inside a CTE Query in SQL Server

Posted on by Ian

A common table expression (CTE) in SQL Server is used to create a temporary result set that can be referenced within a SELECT, INSERT, UPDATE, or DELETE statement. A CTE can simplify complex queries and improve readability. However, there are specific rules for using the ORDER BY clause inside a CTE.

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Using INSERT INTO with a CTE in SQL Server

Posted on by Ian

Common Table Expressions (CTEs) are a useful way to simplify complex queries in SQL Server (and other SQL databases). More often than not, we’ll see CTEs that are used by SELECT statements, but this isn’t necessarily required. CTEs can be followed by SELECT, INSERT, UPDATE, DELETE, or MERGE statements.

This article provides a simple example of using INSERT INTO with a CTE in SQL Server.

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Fix Error “No column name was specified for column…” in SQL Server (Error 8155)

Posted on by Ian

If you’re getting an error that reads something like “No column name was specified for column 2 of ‘SalaryTotals’” in SQL Server, it could be that you’re running a subquery or CTE, but you’re not providing a column name for an aggregate function, or for the XML or JSON result of the CTE.

To fix this issue, use an alias to define a column name for all aggregate functions and XML/JSON outputs in the subquery or CTE. Or if it’s a CTE, you can specify the column name using the CTE syntax.

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Using a CTE with a DELETE Statement in SQL Server to Remove Duplicates

Posted on by Ian

Common Table Expressions (CTEs) are a nifty SQL feature that allow us to define a temporary result set, which can then be used in subsequent queries, including DELETE statements. In the context of removing duplicate data, a CTE can be helpful when we want to identify and remove only the duplicated rows, keeping one version of each unique record.

Let’s go through a step-by-step example of using a CTE with a DELETE statement to remove duplicate data.

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Understanding Common Table Expressions (CTEs): A Beginner’s Guide

Posted on by Ian

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.

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Fix Error “The ORDER BY clause is invalid in views, inline functions, derived tables, subqueries, and common table expressions…” in SQL Server (Error 1033)

Posted on by Ian

If you’re getting an error that reads “The ORDER BY clause is invalid in views, inline functions, derived tables, subqueries, and common table expressions, unless TOP, OFFSET or FOR XML is also specified” in SQL Server, it appears that you’re using the ORDER BY clause in a place that it must also be accompanied by a TOP, OFFSET or FOR XML clause, but you’re not including one of those clauses.

To fix this issue, be sure to include one of those clauses in your query if you need to use the ORDER BY clause.

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