שאלות ותשובות - Wet Ex' Frequently Asked Questions - Wet Ex' Вопросы и Ответы - Wet Ex' أسئلة وأجوبة - Wet Ex'

		.. (לתיקייה המכילה)

Now you explicitly allowed use of views - so can I now write queries using subqueries in the WHERE part?

No, please stick to the course material.

When printing the Table of persons in check_remove what should we print when we reach a NULL entry?

'null'

Can we assume that when we add new tuples to a table they are being added at the end ( which means as the last tupples after adding) ?

No, there's no order in tuples (table) only in queries.

In "check_remove": consider the following DB content: <pre> pid | pname | pcity | edept | mdept --------+----------------+------------+-------+------- 456789 | Sagi Elbaz | Haifa | 10 | 20 456789 | Sagi Elbaz | Haifa | 30 | 10 456789 | Sagi Elbaz | Haifa | 30 | 20 456789 | Sagi Elbaz | Haifa | 10 | null </pre> Now we run the following test: wet 456789 check_remove 10 There are several ways to represent the resulting DB. What should be the output?

First of all, notice that the given DB is legal, since all the requirements are OK. When we run "check_remove 10", the output should be: pid | pname | pcity | edept | mdept --------+----------------+------------+-------+------- 456789 | Sagi Elbaz | Haifa | 30 | 20 456789 | Sagi Elbaz | Haifa | 30 | null 456789 | Sagi Elbaz | Haifa | null | 20 The general guideline is to leave tuples that are not affected by the operation as they were before. You should not merge or separate tuples in check_remove. Just make sure that the obtained content answers the requirements (no identical tuples, no null-null unless no other tuples with same pid, etc.). The meta-algorithm could be: (1) replace all instances of Y by 'null' (2) make sure that the obtained DB content is legal (remove tuples if needed). Of course, the table itself shouldn't be changed, as explained in the assignment.

if we get a command with wrong id number (not an employee and not a manager) and a wrong command (for example: wet 123123 LikesBeer) what error message should we write ? ILLEGAL_EMP_MNG or ILLEGAL_COMMAND

ILLEGAL_EMP_MNG

What should we do in the following case: wet 123123 neighbors 123123 (say it is employee mode).

Print 123123

What happens if you work in employee mode and get 3 arguments (in neighbors for example)? Is it ILLEGAL_COMMAND (wrong number of arguments for this command in employee mode) or is it ILLEGAL_MODE (employee trying to do a manager's function)?

ILLEGAL_MODE

What should be the result of the command: wet 123456 neighbors (Edept = NULL & Mdept != NULL) nothing or just 123456 or everybody (empty condition) ?

Only 123456