Tag: create query

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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Fix “Unknown table … in HANDLER” in MySQL (Error 1109)

Posted on by Ian

If you’re getting MySQL error 1109 which reads something like “1109 (42S02): Unknown table ‘products’ in HANDLER” in MySQL, it appears that you’re trying to reference a table that’s not currently open when using MySQL’s HANDLER statement.

This can happen when you try to read from a table that you haven’t yet opened. It can also happen when you’ve assigned an alias to the table but you try to reference it without the alias. And it can happen if you try to close a table that isn’t actually open.

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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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Possible Reason You’re Getting Error 156 When Running a Subquery in SQL Server

Posted on by Ian

Error 156 in SQL Server is a generic error that doesn’t tell us much, other than the fact that we’re using the wrong syntax.

But if you’re running a subquery, and you’re getting error 156, which reads “Incorrect syntax near the keyword ‘WHERE’.” or whatever keyword it’s near, it could be that you haven’t declared an alias for the subquery.

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A Possible Cause for the 102 Error When Running a Subquery in SQL Server

Posted on by Ian

If you’re running a subquery in SQL Server, but you’re getting error 102 that reads something like “Incorrect syntax near ‘;’“, there could be any number of reasons, because this is a generic error that simply means wrong syntax.

But one possible cause could be that you haven’t declared an alias for the subquery.

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Possible Reason You’re Getting an Error When Using HANDLER … LAST or PREV in MySQL

Posted on by Ian

If you’re getting an error when specifying LAST or PREV for MySQL’s HANDLER statement, it could be that you’re trying to do a table scan using the index syntax.

While the HANDLER statement does accept the LAST and PREV options, we can only use them with an index.

So to fix this issue, be sure to specify an index when using the LAST and PREV options.

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Possible Reason You’re Getting an Error When using a Qualified Table Name with MySQL’s HANDLER Statement

Posted on by Ian

If you’re getting MySQL error 1064 which reads something like “1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ‘READ FIRST’ at line 1” when using the HANDLER statement in MySQL, it could be that you’re qualifying the table with the database name when trying to read from or close a table.

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Fix “Ambiguous column name” in SQL Server (Error 209)

Posted on by Ian

If you’re getting an error that reads “Ambiguous column name“, followed by a column name, in SQL Server, it could be that you’re performing a join on two tables, but you’re not using the table names or aliases when referring to columns within those tables.

To fix this issue, be sure to qualify the columns with their table names or aliases.

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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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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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