Database Management Systems
Some DBMSs have functions that allow us to format numbers as currency just by passing the appropriate format string. This converts the number to a string with the applicable currency symbol, group separator, and decimal point (if relevant).
Other DBMSs don’t make it that easy, and you need to do a bit of work first.
Below are examples of using SQL to format numbers as currency in some of the most popular DBMSs.
Continue readingSQL Server has three recovery models; simple, full, and bulk logged. Each database uses one of these settings.
Backup and restore operations occur within the context of the recovery model of the database
You can change the recovery model of a database by using the ALTER DATABASE statement along with the SET RECOVERY option.
In MariaDB, you can use the SUBSTRING_INDEX() function to return everything before or after a certain character (or characters) in a string.
When using psql with PostgreSQL, we can use the \list+ command to return information about all databases on the server.
We can also use the short form (\l+) to achieve the same result.
In most cases, concatenating a string and a number in SQL is no different to concatenating two strings.
Most DBMSs will concatenate the string and number as if they were both strings. This is because the number is usually converted to a string before the concatenation operation.
Continue readingYou can use the following views to return a list of views in Oracle Database.
Continue readingWhen using psql to run queries against PostgreSQL, we can use the \pset border and \pset linestyle commands to change the border of the table that displays our results.
Some RDBMSs have a GROUP_CONCAT() function that allows you to return a query column as a delimited list (for example, a comma separated list). MySQL and MariaDB are two that have such a function.
PostgreSQL and SQL Server have similar functions called STRING_AGG().
Oracle, on the other hand, has the LISTAGG() function that does pretty much the same thing (and perhaps more).
So you could say that LISTAGG() is Oracle’s GROUP_CONCAT() equivalent.
In SQLite, we can query the sqlite_schema table to find out whether a given table exists.
Prior to SQLite version 3.33.0, this table was referred to as sqlite_master (it can still be referred to as such in subsequent releases for backwards compatibility).
We can use the FORMAT() function in MySQL to format numbers into a more human readable format.
The function returns the number as a formatted string. It adds thousands separators and a decimal separator as required, and rounds the results to the given decimal position.
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