If you’re getting an error that reads something like “The CREATE UNIQUE INDEX statement terminated because a duplicate key was found for the object name” it’s probably because you’re trying to create a UNIQUE constraint on a column that already contains duplicate values.
What is a UNIQUE Constraint?
A UNIQUE constraint is a rule we apply to one or more columns in a database table to ensure that the values in those columns are unique across all rows. This means that no two rows in the table can have the same value(s) in the column(s) where we’ve applied the UNIQUE constraint. It’s an essential tool for maintaining data integrity and preventing duplicate entries in our database.
List of Array Functions in PostgreSQL
Below is an alphabetical list of functions that we can use when working with arrays in PostgreSQL.
Continue readingHow to Create an Array Column in PostgreSQL
PostgreSQL allows us to create arrays and store them in a database column. When we do this, we can use various array related tools to retrieve data from such arrays, as well as manipulate the data within them.
We do need to define the column as an array column though. If we don’t do this, we will likely run into trouble when we want to retrieve data from the array. For example, we can’t just store an array as the text type and then expect to be able to use subscripts to refer to its individual elements.
Continue readingFix Error “Drop table operation failed on table … because it is not a supported operation on system-versioned temporal tables” in SQL Server
If you’re getting an error that reads something like “Drop table operation failed on table ‘db.dbo.TableName’ because it is not a supported operation on system-versioned temporal tables” in SQL Server, it’s probably because you’re trying to drop a temporal table that still uses system-versioning.
In SQL Server, if a table is defined as a temporal table, we can’t drop it while it’s using system-versioning.
If you really want to drop the table, turn off system-versioning first, then try again.
Continue readingIntroduction to Indexing in SQL
When working with databases, performance can be very important. This is especially true in production environments where the end users expect their queries and reports to be generated within seconds (or even milliseconds).
While blistering fast queries may be the norm with smaller datasets, as our databases grow larger and more complex, it can become much more of a challenge to keep our queries nice and snappy. When working with smaller datasets, it’s often possible to get lightning speed results even when not optimizing for speed. But as the datasets grow larger, we need more efficient tools and techniques to retrieve and manipulate data. One such tool is the index.
Continue readingHow to DROP a Temporal Table in SQL Server
Temporal tables, introduced in SQL Server 2016, provide a powerful way to track historical data changes. However, there may come a time when you need to remove a temporal table from your database.
This article will guide you through the process of dropping a temporal table in SQL Server.
Continue readingCheck Whether a Unicode String is Normalized in PostgreSQL
In PostgreSQL, we can use the ... IS NORMALIZED expression to check whether or not a given Unicode string is in a specified Unicode normalization form.
By default, it checks whether it’s in the NFC form, but we also have the option of specifying NFD, NFKC, or NFKD.
Fix Error 2788 “Synonyms are invalid in a schemabound object or a constraint expression” in SQL Server
If you’re getting SQL Server error 2788 that reads “Synonyms are invalid in a schemabound object or a constraint expression” it seems that you’re trying (whether intentionally or not) to create a schemabound object that includes a synonym in its definition, or a constraint with a synonym in its expression.
Continue readingUsing UPDATE with a Subquery in SQL
Ever found yourself needing to update a bunch of rows in your database, but the condition for the update depends on data from another table? That’s where UPDATE with a subquery comes in handy. Let’s break it down.