Texis uses a query language that gives users access to data stored in a relational database. The data manipulation component of this language enables a user to:
In this and the next two chapters, we will review the query capabilities of Texis. In Chapter here, we will study the update, insert, and delete features of the language.
After the tables have been created and loaded with data, you can answer requests for information from a database without the help of professional programmers. You write a question, also called a query, that consists of a single statement explaining what the user wants to accomplish. Based on this query, the computer retrieves the results and displays them. In this chapter you will study some of the simpler ways to form queries.
In Texis, you retrieve data from tables using the
which consists of one or more
WHERE blocks. The structure
of this statement, in its simplest form, consists of one block
containing three clauses:
WHERE. The form of this
SELECT column-name1 [, column-name2] ...
[WHERE search-condition] ;
[ ]' surrounding a clause means the clause is