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

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Non-repeatable reads: This occurs when a transaction tries to read the same row multiple times and gets different values each time due to concurrency. This happens when another transaction updates that data and our current transaction fetches that updated data, resulting in different values. The required query is: Select LTRIM(DEPARTMENT) from Worker; Q-8. Write an SQL query that fetches the unique values of DEPARTMENT from the Worker table and prints its length.

LEFT (OUTER) JOIN: Retrieves all the records/rows from the left and the matched records/rows from the right table. This one might seem more complicated, but it’s still a basic SQL query. It is used when you want to show the total values for each group but you want to include only specific rows in the sum. QueryA table is an organized collection of data stored in the form of rows and columns. Columns can be categorized as vertical and rows as horizontal. The columns in a table are called fields while the rows can be referred to as records. 7. What are Constraints in SQL? Are you looking to boost your data management or analytical abilities? Then you need to know how and where to practice SQL, the worldwide language for managing and running relational databases.

Again, the approach is similar to earlier examples. To select two columns, you need to write their names in SELECT. The important thing is that the columns need to be separated by a comma. You can see in the example that there’s a comma between the columns first_name and last_name.Width sensitivity: Same character represented in single-byte (half-width) and double-byte (full-width) are treated differently. Exercise: Select the columns movie_title, imdb_rating, and year_released from the table movies. Show movies that have the word ‘Godfather’ in the title. Isolation: This property ensures integrity of transaction that are visible to all other transactions. Each of the exercises works off a sample data set and includes an SQL editor which is just a text box with a Submit button. The exercises include a solution which shows the correct query and the output.