Dml helps you add change and delete information in a

This preview shows 13 out of 14 pages.

DML: Helps you add, change, and delete information in a database. It also allows us to view tables, create reports, and create queries [using Query by Example interface (QBE) or structured query language (SQL)]. A Database Query is a “question” that you ask your database. The answer is a virtual table (with data that is potentially from multiple tables). How does one create queries? 13
Image of page 13

Subscribe to view the full document.

a) Querying by example (QBE): show the DBMS what your answer should look like b) Querying using a structured query language (SQL) SQL (Structured Query Language) is the most popular query language used to request information. SQL allows people to perform complicated searches by using relatively simple statements or key words. (Typical commands: SELECT (to specify a desired attribute), FROM (to specify the table to be used), WHERE (to specify conditions to apply in the query). We will be using QBE rather than SQL to do queries as it is much easier and does not require a user to learn SQL syntax (see the screenshot below for an example). To view specific fields (say ISBN, author_firstname, and price) of records that meet a given criteria (say price is greater than 30) from the data contained in the book table, we need to just select the right fields from the specified table and provide the condition for selection of rows as shown below. We will be learning about how to use QBE in the tutorials. 14
Image of page 14
You've reached the end of this preview.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern