SQL provides simple and powerful tools for operating on aggregate data. Aggregate functions operate on groups of rows, rather than individual rows.
- [Instructor] Aggregate data is information … derived from more than one row at a time. … SQL has powerful features for dealing with aggregate data. … Here we're using the world database, … and I have this simple query that you've seen before, … using the count function. … And when we execute this, the result is … a count of 239 rows … in the country table. … Count is an aggregate function. … It returns a single value from a query … that spans many rows of data. … For example, if you want to know how many countries … are represented in each region, … this is where you start seeing the power … of aggregate functions in SQL. … I can say select region, comma, … count … from country. … And I can say group by … region. … The group by clause groups the results … before calling the aggregate function, in this case, count. … This allows you to apply the aggregate function … to groups of data rather than the entire query. … So when I execute this, you see the group by clause … specifies the region column, …
This course was created by Bill Weinman. We are pleased to offer this training in our library.
- How databases are organized
- Selecting rows and columns
- Creating new tables
- Inserting and updating data
- Sorting and filtering
- Accessing related tables with JOIN
- Working with strings
- Understanding numeric types
- Using aggregate functions and transactions
- Automating data with triggers
- Creating views
- Using CRUD functions
Skill Level Beginner
2. SQL Overview
3. Fundamental Concepts
7. Dates and Times
Dates and times2m 6s
11. Views and Subselects
12. A Simple CRUD Application
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