Tag: create query

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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Prepared Statements in MySQL: A Complete Guide with Examples

Posted on by Ian

In MySQL, prepared statements are a feature that allows us to execute the same SQL query multiple times with different parameters. They can improve performance, make our code cleaner, and help defend against SQL injection attacks.

In this article, we’ll explore prepared statements in MySQL, with examples and practical tips on how to use them effectively. We’ll also cover the importance of deallocating statements to free up resources.

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How to Use the HANDLER Statement in MySQL for Faster Data Access

Posted on by Ian

The HANDLER statement in MySQL provides a low-level mechanism to directly access storage engine-level functionality, bypassing some of the overhead associated with regular SQL queries. It can be especially useful for traversing a database in high-performance scenarios.

HANDLER is available for MyISAM and InnoDB tables, and can be used as a faster alternative to the SELECT statement.

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Fix “The objects … in the FROM clause have the same exposed names” in SQL Server (Error 1013)

Posted on by Ian

If you’re getting an error that reads something like “The objects “employees” and “employees” in the FROM clause have the same exposed names. Use correlation names to distinguish them’” in SQL Server, it could be that you’re trying to do a self-join without assigning table aliases.

When doing self-joins, we need to provide aliases for the tables so that SQL Server can distinguish between each instance.

To fix this issue, be sure to use unique table aliases in your query.

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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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Fixing Error 258 “Cannot call methods on nvarchar(max)” When a Subquery Uses FOR XML in SQL Server

Posted on by Ian

If you’re running a subquery that uses FOR XML to produce XML in SQL Server, but you’re getting error 258, which reads “Cannot call methods on nvarchar(max)” it might be that you’re trying to query the XML in the outer query, but your inner query 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 subquery outputs the result using the xml data type.

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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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Fix “The correlation name … is specified multiple times in a FROM clause” in SQL Server (Error 1011)

Posted on by Ian

If you’re getting an error that reads something like “The correlation name ‘a’ is specified multiple times in a FROM clause’” in SQL Server, it could be that you’re doing a join on two tables, but you’re assigning them the same aliases.

Each table’s alias must be unique.

To fix this issue, be sure to use unique table aliases in your query.

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Prepared Statements in PostgreSQL: A Complete Guide

Posted on by Ian

Prepared statements are a feature in PostgreSQL that can improve performance and security when executing repetitive SQL queries.

By creating a prepared statement, the server can parse and plan the query once and reuse it multiple times, leading to faster execution. Prepared statements also help in preventing SQL injection attacks by safely handling user input.

In this article, we’ll explore prepared statements in PostgreSQL, discuss how to create and use them, and cover other important considerations such as query planning and cleaning up statements.

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3 Quick Examples of SQL Subqueries in the WHERE Clause

Posted on by Ian

SQL subqueries are like little helpers that fetch data for our main query. They’re super handy when we need to filter our results based on some other data in our database.

Probably the most common placement of a subquery in SQL is in the WHERE clause. Placing a subquery in the WHERE clause allows us to compare a column against a set of rows that match a certain criteria.

Let’s look at three quick examples of subqueries in the WHERE clause.

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