Database glossary. (Compute's Getting Started With: Databases)
by Tom Campbell
database. See DBMS.
dBASE compatibility. This usually refers to the ability of a program to use or create data files in dBASE's DBF format. Usually, DBFs don't include memo fields or indexes. The term can also refer to full dBASE for DOS language, memo file, and index compatibility. FoxPro, CA-dBFast, and CA-Clipper are all products that can run mst dBASE for DOS programs unchanged, and can also use their memo files and indexes.
DBMS. Short for DataBase Management System. This is different from a database, which is usually information that can be stored in categories, such as names, addresses, and phone numbers. Lately databases are being called tables to emphasize the theoretical view of data as rows and columns and to set aside the term database as an unbrella for the all-encompassing database application.
field. If you imaging data in tabular format with column headings such as Last Name, First Name, and ZIP code, the fields are the columns. Most database managers, require that you give fields a maximum width for efficiency; free-form database managers aren't as fast but will allow virtually any amount of text in any field.
index. A means of sorting records by a particular field and speeding search functions. An index is a copy of one or more fields kept in memory--for example, all the last names or all the states. Searching an index is much faster that searching a disk-based table, but it consumes extra RAM.
memo field. Most fields in a database are of fixed size--a 30-character last name, an eight-byte numberic field, a two-byte time field, and so on. Memo fields let you store arbitrary amounts of information, usually textual, without wasting space on the disk for records that don't have such information. Useful for recording patient histories, special directions, and lately more exotic values such as images and sound.
record. If you imagine data in tabular format, with column headings such as Last Name, First Name, and ZIP code, the records are the rows. Think of a record as being similar to a driver's license. The information on each driver's license varies, but the format (its field layout) is the same on all licenses.
report. Selected information in a database printout. For example, if you print out the names of customers who haven't paid yet, you're generating an accounts receivable report.
row. A less common name for record.
runtime. A means of distributing just enough of the database manager so that it can run your programs but not enough so that the user can create new programs with it. This allows you to create database applications and give or sell them to other people. Normally, the runtime costs extra.
seek. The term used for positioning a disk to a specified place. This may seem lkke a irrelevant issue, but the performance of any database hinges on seek issues. The fastest databases have great indexing schemes, require fields to be of a fixed length, or use a combination of these schemes, any of which can maximize seek time.