Database Management Systems
In SQL Server, a filtered index is a special type of index that only includes a subset of rows from a table or view, based on specified filter criteria.
This criteria would match the criteria of some of the most commonly run queries on the table, thereby helping to improve the performance of those queries.
Below is an example of creating a filtered index in SQL Server.
Continue readingIf you’re getting SQL Server error Msg 129 that reads “Fillfactor 0 is not a valid percentage; fillfactor must be between 1 and 100“, it appears that you’re trying to set the fillfactor of an index to zero.
While it’s true that zero is the default setting, we can’t actually explicitly set the fillfactor to zero when creating or rebuilding an index.
But all is not lost. Below are two solutions to this problem.
Continue readingIf you’ve got a primary key in SQL Server that you need to enable, you’ll need to enable its index. The index is how we enable and disable primary key constraints in SQL Server.
More specifically, we enable a primary key index (and other indexes) by rebuilding them.
Below is an example of enabling a primary key in SQL Server.
Continue readingIf you’re getting SQL Server error 1913 that reads something like “The operation failed because an index or statistics with name ‘IX_Employees_HireDate’ already exists on table ‘Employees’“, it appears that you’re trying to create an index with the same name of one that already exists.
In SQL Server, index names must be unique within a table or view, although they don’t have to be unique within a database. Also, index names must follow the rules of identifiers.
Continue readingWhen we update an array in PostgreSQL, we can update one specific element or we can update a whole slice (a range of elements).
To update a slice, we use a syntax that references the lower and upper bounds of the slice, separated by a colon. We also provide the new values that will be assigned to each element within that slice.
Continue readingSome RDBMSs support an enum type, which comprise a static, ordered set of values. Also known as enumerated types, enum types can be handy for making a column accept just a small set of values, such as days in the week, predefined clothing sizes, or any number of other preset values.
In PostgreSQL, if we want to create a table that uses an enum type, we need to create the enum type first, then apply it against the table. This is a bit different to other RDBMSs such as MySQL, where we don’t need to create the enum type first.
If you’re getting an error that reads “The configuration option ‘fill factor’ does not exist, or it may be an advanced option” in SQL Server, it appears that you’re trying to view or set the default fill factor configuration option.
In SQL Server, fill factor is considered an advanced configuration option. By default, advanced options aren’t available for viewing and changing. However, we can use the following technique to make them available.
One of the various options we have when creating or rebuilding indexes in SQL Server is specifying a fillfactor. If we create or rebuild an index without specifying a fillfactor, then the default fillfactor is applied.
In some cases, using the default fillfactor may be fine, even ideal. In other cases it could be less than ideal, even terrible.
Let’s look at what fillfactor is, how it works, and how we can use it to enhance database performance.
Continue readingIn 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.
If you’re getting SQL Server error 3723 that reads “An explicit DROP INDEX is not allowed on index…” it’s probably because you’re trying to drop a PRIMARY KEY or UNIQUE constraint by dropping its index.