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The SQL SELECT statement returns a result set of rows, from one or more tables. [1] [2] A SELECT statement retrieves zero or more rows from one or more database tables or database views. In most applications, SELECT is the most commonly used data manipulation language (DML) command.
Trying to retrieve a value using the wrong type results in an exception being thrown, which stops code from running further, and slows the application down. This is also true when you use the right type, but encounter a DbNull value ( this can be avoided by using the IsDbNull boolean function of the DataReader class). The benefit to this ...
A prepared statement takes the form of a pre-compiled template into which constant values are substituted during each execution, and typically use SQL DML statements such as INSERT, SELECT, or UPDATE. A common workflow for prepared statements is: Prepare: The application creates the statement template and sends it to the DBMS.
SQL includes operators and functions for calculating values on stored values. SQL allows the use of expressions in the select list to project data, as in the following example, which returns a list of books that cost more than 100.00 with an additional sales_tax column containing a sales tax figure calculated at 6% of the price.
For example, it can be invoked where most other intrinsic functions are allowed. This also includes SELECT statements, where the function can be used against data stored in tables in the database. Conceptually, the function is evaluated once per row in such usage. For example, assume a table named Elements, with a row for each known chemical ...
ActiveVFP (also known as AVFP) is a server-side scripting framework designed for Web development to produce dynamic Web pages.Similar to PHP, but using the native Visual Foxpro (VFP) language and database (or other databases like Microsoft SQL and MySQL), ActiveVFP can also be used in Model-View-Controller (MVC) web applications as well as RESTful API.
The embedded SQL statements are parsed by an embedded SQL preprocessor and replaced by host-language calls to a code library. The output from the preprocessor is then compiled by the host compiler. This allows programmers to embed SQL statements in programs written in any number of languages such as C/C++, COBOL and Fortran.
A database table or view is wrapped into a class. Thus, an object instance is tied to a single row in the table. After creation of an object, a new row is added to the table upon save. Any object loaded gets its information from the database. When an object is updated, the corresponding row in the table is also updated.