Starting from MongoDB 4.4, we can now hide indexes from the query plan. This enables us to evaluate the potential impact of dropping an index without actually dropping the index.
If hiding it has a negative impact, we can unhide the index. This saves us from having to drop the index, then recreate it again.
Below are 3 ways to hide an index in MongoDB.
Distinct values are those values with redundant duplicates removed. In other words, distinct values are unique values.
In MongoDB there are a few ways we can return distinct values in a query. This article presents 3 ways to return distinct values in the mongo shell.
MongoDB provides several ways to drop an index or indexes.
To drop a single index, you can use the dropIndex() method.
To drop multiple indexes, you can use either the dropIndexes() method or the dropIndexes administration command.
If you connect to MariaDB using the command line interface, you might sometimes find that your query results are too wide, due to the number of columns being returned, and the data they contain.
Sometimes you might find that the amount of text returned in a database column is too long. You might just want to return a short snippet of that text, followed by an ellipsis or three dots.
Fortunately, this is relatively easy to do in MariaDB.
When you run a query against a MariaDB database, MariaDB uses a bunch of system variables to determine which character set and collation to use whenever queries are run. If the client uses a different character set to the server, then MariaDB can translate it into an appropriate character set and collation.
When sending the query results back to the client, MariaDB can translate these results back to a different character set altogether if required. MariaDB uses system variables to determine which character sets and collations to use at each of these steps.
Here are three ways to show the connection collation in MariaDB.
You can use the T-SQL code below to convert a month number to its corresponding name in SQL Server.
This is for times where you don’t actually have the full date – when all you have is the month number. If you do have the date, then here’s how to get the month name from a date.
You can specify the character set and collation at various levels in MariaDB. You can specify them at the connection level, the server level, the database level, the table level, and the column level.
You can also specify a collation in your queries so that it overrides any collation that has been previously specified at the aforementioned levels.
To set the character set and collation at the database level, use the CREATE DATABASE statement or ALTER DATABASE statement (depending on whether you’re creating the database or modifying it).
Here are three ways to show the server collation in MariaDB.