As shown in the previous chapter of this course, a database is a collection of one or more tables that store data in a structured format. These tables, contain data that is represented by rows and fields. When a database consists of two or more tables, these tables generally contain separate yet related data. MS Access, Interbase or SQL Server use a single file (Access, the *.mdb file) that represents the entire database. On the other hand, Paradox and dBase databases are defined with separate tables and files that represent indexes and table relations. All the files needed to describe a Paradox database are usually stored in a single directory. Delphi, of course, has means of working with both approaches.
With Delphi, we can connect to different types of databases: local or client/server (remote server) database. Local databases are stored on your local drive or on a local area network. Remote database servers usually reside on a remote machine. Types of local databases are Paradox, dBase and MS Access. Types of client/server databases are MS SQL Server, Interbase or Oracle.
如這課程所示，一個(gè)數(shù)據(jù)庫是一個(gè)將數(shù)據(jù)以一定的結(jié)構(gòu)化方式存儲(chǔ)在一個(gè)或幾個(gè)數(shù)據(jù)表中的一個(gè)集合。數(shù)據(jù)以列和行的結(jié)構(gòu)方式存儲(chǔ)在這些表中。 當(dāng)一個(gè)數(shù)據(jù)庫由兩個(gè)或較多個(gè)的表所組成的時(shí)候,這些表通常包含有分開的，但是仍然相關(guān)聯(lián)的數(shù)據(jù)。
MS Access, Interbase or SQL Server 用一個(gè)單一文件 (Access, 類似 *.mdb 的文件) 描述整個(gè)數(shù)據(jù)庫。 另一方面, 以索引和表的關(guān)系描述的文件，用來定義Paradox 和 dBase 數(shù)據(jù)庫。 通常用來描述Paradox 和 dBase 數(shù)據(jù)庫的所有文件被儲(chǔ)存在一個(gè)單一目錄中。因此Delphi 有兩種工作方式。