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Welcome to this blog post on Learning SQL. SQL, or Structured Query Language, is the standard language for dealing with relational databases. In this post, we’ll discuss the fundamental concepts of data types and functions in SQL.
Data Types in SQL
In SQL, each column in a table has a related data type. These data types determine what kind of data can be stored in the column. Here are some common examples:
- INTEGER: a whole number
- VARCHAR: a string of characters
- BOOLEAN: true or false
Example of Data Types
Here’s how you might specify different data types when creating a table in SQL:
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CREATE TABLE Employees ( ID INTEGER, Name VARCHAR(100), HireDate DATE, IsFullTime BOOLEAN ); |
SQL Functions
SQL functions are powerful tools that let you manipulate data. SQL provides many built-in functions that can be used on data in the database. These fall into several types:
- Aggregate functions: performs a calculation on a set of values and returns a single value
- String functions: manipulate and return string values
- Mathematical functions: perform mathematical calculations
- Date functions: manipulate and return dates
Example of SQL Functions
Here’s how you might use SQL functions in a query:
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SELECT AVG(Salary) AS AverageSalary FROM Employees; SELECT UPPER(Name) AS UpperCaseName FROM Employees; SELECT ROUND(Salary) AS RoundedSalary FROM Employees; SELECT YEAR(HireDate) AS HireYear FROM Employees; |
In these examples, AVG, UPPER, ROUND, and YEAR are all SQL functions. They calculate the average of a set of numbers, convert text to upper case, round a number, and extract the year from a date, respectively.
By mastering data types and functions, you can unlock the full potential of SQL for data analysis. Keep practicing with different data types and functions to gain more experience. Good luck and happy coding!