Imagine then the problem that might arise if more than one customer named "Smith" were recorded in the database. For example, suppose a table existed where the customer's last name had been defined as the primary key. Without a primary key it would not be possible to retrieve or delete a specific row in a table because there can be no certainty that the correct row has been selected. Primary keys allow the database management system to identify a specific row in a table uniquely. Alternatively, a customer table may use the customer's social security number as the primary key. For example, a table may use a bank account number column as the primary key. This is known in database terminology as the Primary Key.
Rows are also sometimes referred to as records or entries and these terms can generally be used interchangeably.Įach database table must contain one or more columns that can be used to identify each row in the table uniquely. When a new customer is added to the table, a new row is created and the data for that customer stored in the corresponding columns of the new row. Each entry in a customer table is equivalent to a row in a spreadsheet and each column contains the data for each customer (name, address, telephone etc). Once again, consider the spreadsheet analogy described earlier in this chapter. Each row, in turn, consists of the columns of data associated with the saved record.
Database RowsĮach new record that is saved to a table is stored in a row. A column designed to store numbers would, therefore, be defined as a numerical datatype. For example, the name, address and telephone data fields of a table are all columns.Įach column, in turn, is defined to contain a certain datatype which dictates the type of data the column can contain. It is helpful at this stage to begin to view a database table as being similar to a spreadsheet where data is stored in rows and columns.Įach column represents a data field in the corresponding table.
#JAVA CREATE SQLITE DATABASE ANDROID#
Before delving into the specifics of SQLite in the context of Android development, however, a brief overview of databases and SQL will be covered. This chapter will provide an overview of the SQLite database management system bundled with the Android operating system, together with an outline of the Android SDK classes that are provided to facilitate persistent SQLite based database storage from within an Android application.
#JAVA CREATE SQLITE DATABASE FREE#
With the ever-present risk that the Android runtime system will terminate an application component to free up resources, a comprehensive data storage strategy to avoid data loss is a key factor in the design and implementation of any application development strategy. The importance of persistent data storage becomes even more evident when taking into consideration the somewhat transient lifecycle of the typical Android application. The use of databases is an essential aspect of most applications, ranging from applications that are almost entirely data driven, to those that simply need to store small amounts of data such as the prevailing score of a game. Mobile applications that do not need to store at least some amount of persistent data are few and far between. Purchase the fully updated Android Studio Chipmunk Edition of this publication in eBook ($29.99) or Print ($46.99) formatĪndroid Studio Chipmunk Essentials - Java Edition Print and eBook (PDF) editions contain 94 chapters and over 800 pages
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