Database Management Systems
In MySQL, you can use the IF NOT EXISTS clause of the CREATE TABLE statement to check whether or not a table of the same name already exists in the database.
If the table doesn’t exist, it will be created. If it already exists, it won’t be created.
Here are five ways to check whether or not a table exists in a MySQL database.
In Postgres, we can use the STRING_AGG() function to transform our query results into a comma separated list.
Instead of each value being output in a separate row (as with any regular query), the values are output to a single row, separated by a comma (or some other delimiter of our choosing).
MariaDB includes a RAND() function that returns a random number. More precisely, it returns a DOUBLE precision floating point value v in the range 0 <= v < 1.0.
This is great, but what if you want to generate an integer within a larger range – and a range that you specify?
Fortunately, there’s an easy technique for doing this.
If you get the “operator does not exist: integer || integer” error in PostgreSQL, it’s probably because you’re trying to concatenate two numbers.
If you really want to concatenate two numbers, the easiest way to overcome this issue is to cast at least one of them to a string data type first.
Another way to do it is to use the CONCAT() function.
Below are two options for returning a full list of stored procedures in MySQL.
When formatting dates in Oracle Database, we have the option of using RR and YY to return a two digit year.
These two format elements are similar. The difference is in how they interpret two digits years.
We also have the option of using RRRR and YYYY when returning four digit years.
If you’re trying to back up the transaction logs in a SQL Server or SQL Edge database, but you get an error that states BACKUP LOG cannot be performed because there is no current database backup, you’ll need to perform at least one full backup of the database before you attempt to back up the transaction logs.