Arrays, records and SQL

Overview

One- and two-dimensional arrays indexed from zero, records and fields, and SELECT, FROM and WHERE queries on a small table with worked results.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What is an array?

   Model answer

   An array is a data structure that holds several items of the same data type under one name. Each item is reached by its index.

2. 2

   Why is an array described as a static, fixed-length data structure?

   Model answer

   An array's size is set when it is declared and cannot change while the program runs. The programmer must decide the number of elements in advance.

3. 3

   How many elements does array teams[6] create, and what are its first and last indexes?

   Model answer

   The declaration creates 6 elements. The indexes run from 0 to 5 because arrays are indexed from 0.

4. 4

   After array scores = [12, 7, 19, 4], what is scores[2]?

   Model answer

   The value of scores[2] is 19. Index 0 holds 12, so index 2 is the third item.

5. 5

   After array scores = [12, 7, 19, 4], what does scores[0] = scores[1] + scores[3] do?

   Model answer

   The line stores 11 in scores[0]. The values 7 and 4 are added, and the result replaces the 12.

6. 6

   What is a two-dimensional (2D) array?

   Model answer

   A 2D array stores data in a grid of rows and columns. Each element is reached by two indexes, such as board[1, 0].

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