Chapter 4

SQL

Commercial database systems require more user-friendly query languages. We will look at SQL in detail. Although referred to as query languages, SQL contains facilities for designing and modifying the database.

The relation schemes for the banking example used throughout the new edition of the textbook are:

• Branch-scheme = (bname, bcity, assets)
• Customer-scheme = (cname, street, ccity)
• Depositor-scheme = (cname, account#)
• Account-scheme = (bname, account#, balance)
• Loan-scheme = (bname, loan#, amount)
• Borrower-scheme = (cname, loan#)

• Background
• Basic Structure
  • The select Clause
  • The where Clause
  • The from Clause
  • The Rename Operation
  • Tuple Variables
  • String Operations
  • Ordering the Display of Tuples
  • Duplicate Tuples
• Set Operations
• Aggregate Functions
• Null Values
• Nested Subqueries
  • Set Membership
  • Set Comparison
  • Test for Empty Relations
  • Test for the Absence of Duplicate Tuples
• Derived Relations
  • Views
• Modification of the Database
  • Deletion
  • Insertion
  • Updates
  • Update of a view
• Joined Relations
  • Examples
  • Join types and conditions
• Data-Definition Language
  • Domain Types in SQL
  • Schema definition in SQL
• Embedded SQL
• Other SQL Features