Practical SQL, 2nd Edition: A Beginner's Guide to Storytelling with Data

Product Information

Select the department from the table employees. Then, use the COUNT() aggregate function. In this case, we use the COUNT(*) version, which counts all the rows. We give the column the alias employees_by_department. IF score IS NULL THEN SET total = 0; /* Termination condition */ ELSE CALL calctotal(number + 1); /* Recursive call */ SET total = total + score; /* Action after recursion */ END IF;

Once again, this basic SQL query example is useful when you want to select several columns but not all the rows from the table. Now you want to find the values that are the same as the value from the condition. For that, you need the equality condition ( =). Query The required query is: Select * from Worker where FIRST_NAME like '%a'; Q-18. Write an SQL query to print details of the Workers whose FIRST_NAME ends with ‘h’ and contains six alphabets.After running the above command, if the database creation was successful, then the below message is shown: CREATE DATABASE 5. How can we start, restart and stop the PostgreSQL server?

We select the department, use AVG() with the salary column, and group the output by department. Output department The DELETE command deletes only the rows from the table based on the condition given in the where clause or deletes all the rows from the table if no condition is specified. But it does not free the space containing the table. 33. What are Aggregate and Scalar functions? This example will again demonstrate how to filter output using WHERE. It will be a bit more advanced this time, as we’ll use a logical operator. In SQL, logical operators allow you to test if the filtering condition is true or not. They also allow you to set multiple conditions. The required query is: Select * from Worker where FIRST_NAME not in ('Vipul','Satish'); Q-15. Write an SQL query to print details of Workers with DEPARTMENT name as “Admin”.Write Ahead Logging is a feature that increases the database reliability by logging changes before any changes are done to the database. This ensures that we have enough information when a database crash occurs by helping to pinpoint to what point the work has been complete and gives a starting point from the point where it was discontinued. We hope you enjoyed solving the SQL exercises and learned something new along the way. Stay tuned for our next post, where we’ll bring you even more challenging SQL query questions to sharpen your proficiency. In other words, the values in the column first_name have to be equal to Luca. Also, when the condition is not a number but a text or a date/time, it has to be written in single quotes ( ''). That’s why our condition is written as ' Luca', not simply Luca. Output

Unbelievable as it may seem, this story is true. This woman came from a very underprivileged Southeast Asian nation, and the opportunity to practice her computer skills simply had never arisen during her six long years as a computer science student.LEFT (OUTER) JOIN: Retrieves all the records/rows from the left and the matched records/rows from the right table. We can achieve this by using the pg_dump tool for dumping all object contents in the database into a single file. The steps are as follows: In general, this table is a list of each quarter’s sales made by every employee shown in the first table. This updated second edition has been thoroughly revised to reflect the latest in SQL features, including additional advanced query techniques for wrangling data. This edition also has two new chapters: an expanded set of instructions on for setting up your system plus a chapter on using PostgreSQL with the popular JSON data interchange format.