Some RDBMSs provide an easy way for us to find out how many rows were affected by the last SQL statement. This can be handy when running INSERT, UPDATE, or DELETE statements.
The method used depends on the DBMS we’re using. Below, I look at how some of the major DBMSs implement this functionality.
Continue readingSQL Server provides us with both a @@ROWCOUNT and a ROWCOUNT_BIG() function. You may be wondering what the difference is between these two functions?
Let’s find out.
Continue readingIn MySQL, BENCHMARK() is a built-in function that executes an expression repeatedly for a specified number of times.
It can be used to time how quickly MySQL processes the expression. Specifically, the function is intended for measuring the runtime performance of scalar expressions.
The result is always 0, or NULL for inappropriate arguments. The function is intended to be used within the mysql command line tool, which reports query execution times.
If you’re getting SQL Server error Msg 529 that reads Explicit conversion from data type date to int is not allowed, it’s because you’re trying to explicitly convert a date data type to an int data type, which is not allowed in SQL Server.
To fix this issue, try converting the date value to a string first, and then to an integer.
Alternatively, change the destination type to one that’s allowed.
Also, check that you’re trying to convert the correct value. For example, you may have selected the wrong column or variable. In this case, selecting the correct column may fix the problem.
Continue readingIn the world of database management systems (DBMSs) and computer programming, CRUD is an acronym that stands for Create, Read, Update, and Delete. These are considered to be the four basic operations of persistent storage.
Let’s take a look at how CRUD fits into database management systems and programming in general.
Continue readingIf you’re getting an error that reads something like “START value (11) cannot be greater than MAXVALUE (10)” in PostgreSQL when you’re trying to create a sequence, it’s because your sequence’s start value is higher than its maximum value, when it should be lower or the same.
To fix this issue, be sure that the sequence’s maximum value is not less than its start value.
Continue readingBy default, time zone names aren’t included with MySQL. The MySQL installation process creates the appropriate tables, but it doesn’t populate these tables.
That said, it’s very easy to populate these tables.
Once populated, we can list out the time zone names available in our system by querying the mysql.time_zone_name table.
In MySQL and MariaDB we can use the AUTO_INCREMENT keyword to create an automatically incrementing column in a table. In SQLite, we’d use the AUTOINCREMENT keyword. And in SQL Server we can use the IDENTITY property. Some of those DBMSs also allow us to create sequence objects, which provide us with more options for creating an auto-increment type column.
When it comes to PostgreSQL, there are a few ways to create an auto-incrementing column. Below are three options for creating an AUTO_INCREMENT style column in Postgres.
In MySQL, COLLATION() is a built in function that returns the collation of its string argument.
We provide the string when we call the function.
Continue readingIn MySQL, CHARSET() is a built in function that returns the character set of its string argument.
We provide the string when we call the function.
Continue reading