When working with databases, sometimes you want to find out how many rows will be returned by a query, without actually returning the results of the query. Or sometimes you might just want to find out how many rows are in a given table.
In SQL Server, you can use T-SQL‘s COUNT() function to return the number of rows that would be returned in a query.
In MySQL, you can check the size of all tables within a given database (or on all databases) by querying the information_schema.tables table. This table stores data about each table in a database, including information about each table’s size, creation date, collation, etc.
You can also find the size of each table within a database by using the MySQL Workbench GUI.
This article provides a quick overview of each method.
In MySQL, you can query the information_schema.tables table to return information about the tables in a database. This table includes information about the data length, index length, as well as other details such as collation, creation time, etc. You can use the information in this table to find the size of a given database or all databases on the server.
You can also use the MySQL Workbench GUI to find details about the database (including its size).
This article provides a quick overview of both methods.
When using MySQL, you can use the AVG() function to calculate the average value from a range of values.
For example, you can use this function to find out what the average city population is for a given country or state. Given a country will have many cities, each with different populations, you can find out what the average is between them. One city might have a population of say, 50,000 while another has a population of 500,000. The AVG() function will calculate the average for you.
You might have noticed that T-SQL includes both a CONVERT() function and a TRY_CONVERT() function that you can use in SQL Server to perform conversions between data types. But if you’re scratching your head over what the difference is between these two functions, read on!
The difference between CONVERT() and TRY_CONVERT() is in the way they handle data types that can’t be converted. One throws an error, while the other returns null. The following examples demonstrate this.
When converting between data types in SQL Server, you will run into various functions that seemingly do the same thing. However, there are usually differences between these functions that might not be apparent at first glance. An example of this is the difference between the CAST() and TRY_CAST() functions.
This article demonstrates the difference between these functions when using SQL Server.
If you’ve ever tried to concatenate a string with a number while using SQL Server, but received an error, this article should clear things up for you. There’s more than one way to perform concatenation using T-SQL in SQL Server, and if you’re concatenating different data types (like a string and a number) then you may receive an error, depending on how you do the concatenation.
The thing to remember when concatenating different data types is that they need to be converted into the same data type first. More specifically, when concatenating a string with a number, the number will need to be converted to a string before it can be concatenated with the string. Fortunately SQL Server/T-SQL makes this a breeze.
This article presents six ways to concatenate strings with numbers using T-SQL.
This article presents two methods for converting a decimal number to its hexadecimal equivalent in MySQL.
More specifically, I present two functions that enable you to do this conversion. The two functions are as follows:
HEX() functionCONV() functionBelow is an explanation of each function.
In MySQL, you can convert a string to its hexadecimal representation by using the HEX() function.
The HEX() function works on both strings and numbers, however, its handling of each of these is slightly different. When used to convert a number, it returns a hexadecimal string representation of the number treated as a longlong (BIGINT) number. But when converting a string, it returns a hexadecimal string representation of the string where each byte of each character is converted to two hexadecimal digits.
MySQL includes various functions that can assist you when working with hexadecimal values. One of the most obvious functions is the HEX() function, which enables you to convert a string into its hexadecimal equivalent.
However, there may be times where you want to convert a hexadecimal string back to a more readable string. That’s what this article is about.
Here are three ways to “unhex” a string in MySQL:
UNHEX() functionX hexadecimal notation0x notationBelow are examples of each of these methods.