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:
- Write queries to retrieve information from the database.
- Modify existing data in the database.
- Add new data to the database.
- Delete data from the database.
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] ;
- The "..." above indicates additional column names can be
- Brackets `
[ ]' surrounding a clause means the clause is
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