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To process this statement without an index the database software must look at the last_name column on every row in the table (this is known as a full table scan). With an index the database simply follows the index data structure (typically a B-tree ) until the Smith entry has been found; this is much less computationally expensive than a full ...
Comma-separated values (CSV) is a text file format that uses commas to separate values, and newlines to separate records. A CSV file stores tabular data (numbers and text) in plain text, where each line of the file typically represents one data record.
A scalar function returns only a single value (or NULL), whereas a table function returns a (relational) table comprising zero or more rows, each row with one or more columns. User-defined functions in SQL are declared using the CREATE FUNCTION statement. For example, a user-defined function that converts Celsius to Fahrenheit (a temperature ...
In Pascal, the command with R do S would execute the command sequence S as if all the fields of record R had been declared as variables. Similarly to entering a different namespace in an object-oriented language like C# , it is no longer necessary to use the record name as a prefix to access the fields.
Within the Eiffel software development method and language, the terms argument and parameter have distinct uses established by convention. The term argument is used exclusively in reference to a routine's inputs, [ 7 ] and the term parameter is used exclusively in type parameterization for generic classes .
drop ondrop The drop event is fired on the element where the drop occurs at the end of the drag operation. Yes Yes dragend ondragend The source of the drag will receive a dragend event when the drag operation is complete, whether it was successful or not. Yes No Keyboard keydown onkeydown Fires before keypress, when a key on the keyboard is ...
An anaphoric macro is a type of programming macro that deliberately captures some form supplied to the macro which may be referred to by an anaphor (an expression referring to another). Anaphoric macros first appeared in Paul Graham's On Lisp and their name is a reference to linguistic anaphora—the use of words as a substitute for preceding ...
The same technique can be used to map two-letter country codes like "us" or "za" to country names (26 2 = 676 table entries), 5-digit ZIP codes like 13083 to city names (100 000 entries), etc. Invalid data values (such as the country code "xx" or the ZIP code 00000) may be left undefined in the table or mapped to some appropriate "null" value.