The concept of line-editing goes way back to the days when all many people had to work with were dumb terminals that didn't allow full-screen editing, and connection speeds were so slow that full-screen editing would have been very painful anyway. A good line editor will allow you to work productively at connection speeds as low as 300 bits per second. While working at that speed isn't much of a concern today, it accurately reflects the environment at the time SQL*Plus was first conceived.
The line-editing process in SQL*Plus follows these steps:
Enter a SQL statement or PL/SQL block, which SQL*Plus stores in the buffer.
List the contents of the buffer to the screen.
Enter SQL*Plus commands telling SQL*Plus to make changes to the statement or block in the buffer.
List the buffer again.
If you like what you see, execute the statement or block; otherwise, you go back to step 3 and make some more changes.
I can remember that in my younger days my fellow programmers and I always took great pride in the number of line-editing changes we could make and visualize in our heads before we had to break down and list our code again.
When working with the line editor in SQL*Plus, you must understand the concept of the current line. The current line is the one that you have most recently "touched." When you are entering a statement, the most recently entered line is the current line.
The statement shown in Example 2-9 is six lines long. Line 7 doesn't count and is not added ...