SQL Server Tutorial: Implicit conversion

Want to learn more? Take the full course at https://learn.datacamp.com/courses/functions-for-manipulating-data-in-sql-server at your own pace. More than a video, you'll learn hands-on coding & quickly apply skills to your daily work. --- Now that you have an idea what are the most common data types in SQL Server, let's discuss how to convert data from one type to another. There is an important rule you need to keep in mind: for comparing two values, they need to have the same data type. If they are different, there are two options: SQL will try to convert one type to the other behind the scenes. This is called implicit conversion. If that's not possible, you need to explicitly convert them, using the functions CAST() or CONVERT(). Let's start with some examples and figure out what conversions can be done automatically. Say you have this simple query from the "ratings" table. The "cocoa_percent" is a decimal column. You want to restrict the results, adding a WHERE clause to compare the percentage to several values. This code obviously works and will return a list with all the percentages greater than 0.5. Comparing a decimal to an integer is also possible. What do you think will happen when executing this query? It will work and the "cocoa_percentage" will be implicitly converted from decimal to datetime. The value 0 corresponds to the date "01-01-1900". Adding 1 to the decimal number will add one day when it's converted to a datetime. Converting the number 365 to datetime will produce the date "01-01-1901". This query, however, will generate an error, because the server cannot understand what we want to achieve by comparing the letter "A" to a decimal column. And last but not least, let's do the comparison with the character "0.5". Surprisingly, this query will work. The difference between this and the previous query, is that the character "0.5" can be interpreted by SQL Server as a number and is implicitly converted. For every comparison present in