Category: SQL Server

5 Ways to Return UNIQUE Constraints in SQL Server

Posted on by Ian

In SQL Server, we can use UNIQUE constraints to ensure that a column (or columns) contain only unique values. When we have a UNIQUE constraint against a column, the system will prevent any duplicate values are entered into that column.

Sometimes we need to return a list of UNIQUE constraints, so that we simply know what we’re working with. Other times we might want to create scripts for all of our UNIQUE constraints so that we can recreate the constraints later.

Regardless of the reason, here are five methods for returning UNIQUE constraints in a SQL Server database.

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Possible Reason for Error 1914 “object is not a user table or view” in SQL Server

Posted on by Ian

If you’re getting an error that reads something like “Index cannot be created on object ‘Customers’ because the object is not a user table or view” it could be that you’re trying to create an index, but there’s also a synonym of the same name (but in a different schema). It would appear that SQL Server thinks that you’re trying to create the index on the synonym instead of the table or view of the same name.

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Understanding the BREAK Keyword in SQL Server WHILE Loops

Posted on by Ian

WHILE loops are a powerful feature in most programming languages that allow developers to execute a block of code repeatedly as long as a specified condition is true. However, there are times when we may need to exit a loop prematurely based on certain criteria. SQL Server caters for this possibility with the BREAK keyword.

In this article, we’ll explore how to effectively use the BREAK keyword within WHILE loops in SQL Server.

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Fix Error 156 “Incorrect syntax near the keyword ‘OR'” in SQL Server When Creating a Filtered Index

Posted on by Ian

If you’re getting an error that reads something like “Incorrect syntax near the keyword ‘OR’” when creating a filtered index in SQL Server, it’s probably because you’re using the OR operator in your WHERE clause.

Filtered indexes don’t support the OR operator.

However, filtered indexes do support the IN operator, and so it’s possible to change your query to use that.

So to fix this issue, try the IN operator instead.

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What is a Clustered Index in SQL Server?

Posted on by Ian

There are around a dozen types of index in SQL Server, but the most commonly used index type would have to be the clustered index. By default, a clustered index is automatically created when we create a primary key, and so if your tables have primary keys, then there’s a pretty good chance you’ve got clustered indexes all over your database.

But what exactly is a clustered index?

Let’s delve into what a clustered index is, how it works, its relationship with primary keys, and why it’s so important for our database performance.

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What is a Nonclustered Index in SQL Server?

Posted on by Ian

We’ll often hear SQL Server developers talk about adding indexes to a table to improve the performance of some of the more heavily run queries. Such queries could be quite complex, and/or search through large tables, perhaps with lots of joins, and generally take a long time to complete.

But it’s not just a matter of saying “add an index” and being done with it. We need to decide how to design the index, and even before that, what type of index to add.

Two of the most commonly used index types in SQL Server are the clustered index and the nonclustered index.

In this article, we’ll explore what a nonclustered index is, how it works, and when we should use it to enhance our database performance.

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Fix Error 8655 “The query processor is unable to produce a plan because the index … on table or view … is disabled.

Posted on by Ian

If you’re getting SQL Server error 8655 that reads something like “The query processor is unable to produce a plan because the index ‘PK__Employee__7AD04FF1A39ECAB1’ on table or view ‘Employees’ is disabled“, it’s probably because the clustered index for the table is disabled.

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How to Disable a Primary Key in SQL Server

Posted on by Ian

Under most circumstances, disabling a primary key is a bad idea. A very bad idea. After all, we implement primary keys in the name of data integrity, and by disabling a primary key, we could compromise that effort.

But there may be cases where you need to disable a primary key, for one reason or another. For example, to facilitate data migration efforts, or bulk inserts, to perform certain maintenance tasks, or simply to insert dummy data in your development environment.

Whatever the reason, here’s how to disable a primary key in SQL Server.

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How to Change SQL Server’s Default Fillfactor

Posted on by Ian

Fillfactor is an option that we can set on SQL Server indexes in order to fine tune index data storage and performance. It determines the percentage of space on each leaf-level page to be filled with data, reserving the remainder on each page as free space for future growth.

The default fillfactor can be set as a configuration option. SQL Server sets this value to 0, and so this is what’s used when we create an index without specifying a fillfactor. The value of 0 is actually the equivalent of 100 (or meaning 100%). In other words, by default, the leaf-level pages are filled to capacity.

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