A table is a group of data items arranged in a rectangular array, each row containing the same categories of information. Each data item (row) is called a record. Each category (column) is called a field. Two tables with a common field are said to be related. A database is a collection of one or more tables that are usually related.
Visual Basic's Database Explorer can be used to identify and view the tables of a database.
The DataTable object is used to access the information in a table. This information is supplied via a data adapter. The data adapter must be provided three pieces of informationthe software serving as the database provider, the location of the database, and a statement telling it what part of the database to access. The first two pieces of information are combined into a string called a connection string.
When a list box is bound to a data table, information from the database can be inserted automatically into the list box.
A primary key is a field or set of fields that uniquely identifies each row of a table. The Rule of Entity Integrity states that no record can have a null entry in a primary key. A foreign key is a field or set of fields in one table that refers to a primary key in another table. The rule of referential integrity states that each value in the foreign key must also appear in the primary key.
Structured Query Language (SQL) is used to create a "virtual" table, or view, consisting of a subtable of a table or of a join of two tables and imposes an order on the records. The subtable or join is specified with the reserved words SELECT, FROM, WHERE, ORDER BY, and INNER JOIN ... ON. The WHERE clause of an SQL statement commonly uses the Like operator in addition to the standard operators. Data adapters use SQL statements to specify the views they will use to fill a data tables.
The DataGridView control can show an entire "virtual" table in a spreadsheetlike display. It can also be used to make changes in a database.
A computed column of a data grid does not contain values from a field in a database table, but rather, it contains values that are computed from one or more fields.
