SQL database system
 
Manual page for using(ordinary)

Using ordinary files

An "ordinary file" is a file located anywhere in the unix file system that conforms to the shsql table structure. The shsql table types chart describes how ordinary files differ in their usage from standard database tables.

Ordinary files may reside anywhere in the file system. Ordinary files may be accessed by the SELECT command, in a straight select or a join. They can be created using SELECT INTO, or by other programs. Indexes may be built/rebuilt for ordinary files using the SQL CREATE INDEX command (SELECT can then use the index).

SQL data-modification operations, including INSERT, UPDATE, DELETE, MAINTAIN, and ALTER, can not be applied to ordinary files.


Note

Shsql can be used to access ordinary tabular data files exclusively without using any database tables. However, a config file and (at least a skeleton) database structure must still exist, and the SHSQL_DB environment variable must be set to point to that structure. See the project setup page.


Security concerns

Because this feature allows SHSQL to access any readable file on your file system, avoid situations where table names are built using user-supplied values (such as CGI user variables).. this might allow a hacker to see arbitrary files.


Naming

When referencing an ordinary file in a SELECT or CREATE command the file's full pathname should be used. The first character in the path name must be slash (/) or dot (.).


Usage examples

Here are some examples:

select * from ./trial3/55x25 where intensity > 0.7

select ... into ./lists/problemcases where ...

create index on /home/steve/pubmed/masterlist journal_name






Copyright Steve Grubb  


Markup created by unroff 1.0,    June 02, 2005.